How to find the best energy drink using the 5 Levels of Fatigue

Updated Sept 10, 2019.

What’s the best energy drink? Everyone has their own preferences based on taste, but the scientific truth is “the best energy drink” depends on your body and your situation. Think of it this way:

An energy drink is like your favorite song: what gets YOU pumped up may do nothing for ME. A song that gets you up and moving on a Monday morning is probably not your go-to song to celebrate a Friday night.

Everyone is different, and different situations call for different solutions (that’s a beverage pun right there – in chemistry, a solution is a liquid mixture).

This is a picture of a card I made for a PhD student leaving my lab in grad school. To help her remember me, I drew a self-portrait. Big hair. Music. Caffeine.

I developed the 5 Levels of Fatigue in college and in grad school. I was juggling full-time studies with two part-time jobs. In addition to studying the science behind energy drinks, I was drinking them - a lot.

As a biochemistry major, I knew caffeine would stop working for me if my body got too used to it on a regular basis. Caffeine blocks adenosine, which prevents adenosine from sending you “YOU ARE GETTING SLEE-PY” signals. But after awhile your body realizes caffeine is blocking adenosine and MAKES MORE, so it takes MORE caffeine to feel the same energy boost.

Using the 5 Levels of Fatigue makes it less likely you'll develop caffeine dependence - it means you won't need more and more caffeine to feel awake.

Here's How It Works:

  • Every energy drink has a different amount of caffeine, juice, and sugar.
  • Some energy drinks are carbonated, some are not.
  • Carbonation, juice, and sugar content will all make one energy drink FEEL more powerful than another drink with the same amount of caffeine.

FATIGUE LEVEL 1: Dehydrated & Drowsy

At this level, you’re feeling a little drowsy, but not exhausted or overwhelmed.

SOLUTION = Do something Different. Go for a walk. Switch tasks. Take a 5 min break. Drink WATER. DO NOT drink any caffeine at this level.

Caffeine Informer Bai Antioxidant Infusion caffeine content

FATIGUE LEVEL 2: Too Tired

At this level, “I’m too tired” becomes the excuse for action. You’re not exhausted and not just bored or drowsy. You’re just a little bit off, a little sluggish, a little lethargic. You’re “too tired”.

SOLUTION = A LITTLE sluggish means A LITTLE caffeine. Look for caffeinated beverages with no more than 100 mg caffeine.

  • NON-carbonated beverages will provide a gentler boost because carbonation irritates the stomach lining so caffeine gets absorbed more quickly.
  • TEA-based beverages will also provide a gentler boost because L-Theanine has a calming effect.

FATIGUE LEVEL 3: Stressed & Struggling

At this level, you’re starting to feel overwhelmed. You’re trying to wake up but you’re really struggling to stay focused and engaged. A walk and a cup of tea aren’t going to cut it here, but it’s still not worst-case scenario “energy emergency” quite yet.

SOLUTION = Several scientific studies and international organizations say you should have no more than 200 mg caffeine at a time. So that’s what we’re looking for here.

  • HYBRIDS are the best option here – energy drink/coffee hybrids, energy drink/wannabe Gatorade drinks, caffeinated juice blends
  • Pick carbonated over non-carbonated for an extra boost if needed
  • Pick sugar-free or drinks where the only sugar comes from juice – save the full-sugar versions for those “energy emergencies” at Fatigue Level 4

FATIGUE LEVEL 4: Energy Emergency

At this level, we’re going to ignore health guidelines and go over that 200 mg caffeine per serving recommendation. This is an energy emergency. This is one step short of being a walking zombie. We’re talking just-trying-to-survive, counting-the-hours-before-I-can-go-home crisis.

SOLUTION = Choose a carbonated energy drink with more than 200 mg caffeine per can. You can also pick an energy shot because shots have higher caffeine mg per oz than energy drinks. Energy drinks with sugar will give you an extra boost though you may crash after a few hours so ONLY pick drinks with more than 10 grams sugar if you absolutely need that much more help.

FATIGUE LEVEL 5: Zombie

At this level, no amount of caffeine can save you. This is your absolute breaking point. This is worst-case-scenario.

SOLUTION = Only sleep can save you now.


This is the 5 Levels of Fatigue.

PBR Hard Coffee – Ingredients, Safety, Where to Find It

Pabst Blue Ribbon has released a “Hard Coffee” in select markets. Where can you find it? What is it? What’s in it? Why did Four Loko get in trouble with the FDA for caffeinated alcohol but this drink is okay? Food Scientist GreenEyedGuide answers these questions in this review of PBR Hard Coffee.

Don’t have time to watch the full episode? You can read the highlights below.

PBR Hard Coffee: Ingredients, Safety, and Where to Find It – YouTube Episode

What is PBR Hard Coffee?

PBR Hard Coffee is not a blend of coffee and beer. It’s not a beer with coffee flavoring. According to the PBR website, it’s not even “beer”.

PBR Hard Coffee - "Not Beer" according to PBR website

PBR indicates this is not beer, it’s a flavored malt beverage.

What’s the difference between beer and a flavored malt beverage?

According to Charlie Bamforth, Anheuser-Busch Endowed Professor of Brewing Science from the University of California, Davis:

Beer is an alcoholic beverage made from malted cereal grain, flavored with hops, and brewed by slow fermentation.

According to Beer and Brewing’s online dictionary:

A flavored malt beverage (FMB) is an alcoholic beverage made from original base containing malt, but then stripped of malt character and then flavored. … FMB production starts out much like a beer and then goes through treatment (carbon filtration, reverse osmosis, etc) to remove as much beer and malt flavor and color as possible. The clear, colorless treated malt base is then sweetened, usually with high-fructose corn syrup, and then flavored.

PBR Hard Coffee Ingredients

PBR Hard Coffee ingredients are arabica and robusta coffee beans, creamy milk, and sweet vanilla flavor.

PBR Hard Coffee Caffeine Content

A “standard” cup* of coffee contains 100 mg caffeine. According to CNN (the only ones who had this amount in their coverage), there’s 30 mg caffeine in a can of PBR Hard Coffee.

*NOTE*Please note 100 mg is used as the industry standard. However, it’s common knowledge the actual amount in a cup of coffee varies wildly – researchers even found variation when they bought a cup of coffee from one location on multiple days. [Reference] [GEG Summary]
caffeine amount in Pabst Blue Ribbon (PBR) Hard Coffee compared to Red Bull and a standard cup of coffee - GreenEyedGuide.com

A 12-oz can of Red Bull has 110 mg caffeine – just a little more than a “standard” cup of coffee. PBR Hard Coffee has 1/3 of that amount – containing only 30 mg caffeine per can. The caffeine mg-per-oz amounts of PBR Hard Coffee, a standard cup of coffee, and a 12-oz Red Bull are 3, 13, and 9 mg-per-oz, respectively.

PBR Hard Coffee Alcohol Content

The alcohol content of PBR Hard Coffee is comparible to other flavored malt beverages: Mike’s Hard Lemonade, Henry’s Hard Soda, Truly Sparking, and Smirnoff Ice all have about 4-5% alcohol-by-volume (ABV).

The alcohol content of PBR Hard Coffee is also comparable to a the original PBR can of beer.

Is PBR Hard Coffee safe?

How many cans of PBR Hard Coffee can you drink before it becomes dangerous? In an earlier episode on the GreenEyedGuide YouTube channel, I reviewed the consensus of several different countries regarding mixing caffeine and alcohol.

Screenshot of GreenEyedGuide YouTube Episode: Mixing Caffeine and Alcohol
You can watch this full episode by clicking here

The scientific consensus of the European Food Safety Authority is that you can have up to 200 mg caffeine mixed with enough alcohol to give you a Blood Alcohol Content of 0.08. If you exceed 200 mg caffeine or BAC 0.08, mixing caffeine and alcohol becomes no longer safe**.

*NOTE* For all the side-effects and risks of mixing caffeine and alcohol, see the YouTube Episode above – skip to time stamp 4:51.
Caffeine Informer graphic showing what 200 mg caffeine looks like - 2.5 Red Bull, 1.25 cans of Monster, 6 cans of Coca-Cola, 2.5 cups of coffee.
THIS GRAPHIC from CaffeineInformer.com shows how much caffeine you can safely mix with alcohol.

The graphic above, from Caffeine Informer, shows how much caffeine you can safely mix with alcohol – at 30 mg per can, the caffeine amount in PBR Hard Coffee is very low, so it makes PBR Hard Coffee much safer than something like the original (pre-2010) Four Loko.

Why did Four Loko get in trouble with the FDA but this PBR Hard Coffee is okay?

On the FDA’s information sheet on caffeinated alcoholic beverages, they clarify the reason the manufacturers of caffeinated alcoholic beverages got in trouble is they were adding caffeine to the products. According to the FDA, caffeine is an “unsafe food additive” because it is not approved, at any amount, to be added to alcohol. Adding a natural source of caffeine, however, is just fine.

If you’re curious about FDA regulations around caffeine, this blog post does a good job of explaining the regulations for caffeine in food, drinks, and supplements.

The difference with PBR Hard Coffee is there’s no added caffeine, they’re adding coffee, which is a natural source of caffeine. Hello, loophole? Maybe…

The amount of caffeine in PBR Hard Coffee is so low you’d have to finish 7 cans before the caffeine crosses that 200 mg threshold where it starts interfering with how drunk you feel.

Where can I find PBR Hard Coffee?

This drink is still being tested in select markets – Pabst wants to see how successful this drink is going to be before going all in.

Right now (as of July, 2019) you can only get PBR Hard Coffee in the following states:

  • Pennsylvania
  • Maine
  • New Jersey
  • Florida
  • Georgia

If you live in one of those states, you can use the store locator at this link to find the nearest location of where you can buy it.

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Love this info? Want to learn more?

I’ve researched the science and safety behind energy drinks and their ingredients since 2003. This book is the culmination of my research:

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Caffeine Effects on the Brain – Part 2

Welcome to GreenEyedGuide, your guide to the science behind caffeine and energy drinks. This is a series on How Caffeine Affects the Brain. Since this is a complex topic and we have a lot to cover, I’ve broken the key questions into different posts. In this part, we compare coffee versus energy drinks to determine what makes the best study aid and why.

Later in this series, we’ll also talk about:

  • Why does caffeine work differently after an all-nighter?
  • What ingredients in energy drinks help you focus during gaming?
  • Does your brain get addicted to caffeine and energy drinks?

Coffee Versus Energy Drinks – Which is Better for Studying?

If you don’t have time to watch the full episode, don’t worry! The highlights are below.

Read more

Caffeine Effects on the Brain – Part 1

Welcome to GreenEyedGuide, your guide to the science behind caffeine and energy drinks. This is a series on How Caffeine Affects the Brain. Since this is a complex topic and we have a lot to cover, I’ve broken the key questions into different posts. In Part 1 we’ll discuss how caffeine makes you feel awake and alert, we’ll review the biochemistry (which you can skip), and we’ll summarize the ways caffeine does and does not help you focus.

Later in this series, we’ll also talk about:

  • Why does caffeine work differently after an all-nighter?
  • What ingredients in energy drinks help you focus during gaming?
  • Is coffee or energy drinks better for studying?
  • Does your brain get addicted to caffeine and energy drinks?

Part 1: How does caffeine help you focus?

Read more

Trying Caffeinated Water? Start Here

Caffeinated water can be a great alternative to the stereotypical energy drink, but if you’ve never heard of caffeinated water, where do you start? How do you know if it’s right for you?  This is the third of a three-part series on caffeinated water. In the last two posts in this series, we’ve answered some of the most commonly asked questions about caffeinated water. But now we ask one final question:

  • Where do I start?

In This Series:

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