Coffee Efficiency

There's a drug that you can take, legally, to make you more efficient at your job: Caffeine. It comes in all kinds of foods and drinks, and makes you more alert than napping.
Of course, like any stimulant, your body habituates to its presence. The more you take, the more you need to get the same effect. And more eerily: you only habituate to the alertness that people consume it for. The increasingly unpleasant side effects like jitteriness, insomnia, skipped heartbeats, and irritability, are directly proportional to use.
Caffeine addiction is also fairly easy to gauge: On a day when you don't have to go to work, skip your morning coffee, soda, or chocolate. If you have a massive headache and an incessant urge to go have one anyway, congratulations, you're addicted. (If it's important to you to quit, you can switch to decafs for a while. Same ritual, less psychoactive.) Although, a caffeine addiction isn't a problem unless you have trouble sleeping at night as well. We need sleep: being awake slowly gives us brain damage that only sleeping can repair.
Plants that make caffeine do so to discourage insects and other animals from eating them. We humans survive it mostly by being very large, and keeping our consumption down. (There are web programs that can determine the lethal dose of your favorite beverage of choice. For most people, it's very high but technically possible to consume in one day.)
Caffeine is also highly present. Huge numbers of people start their day with a cup of coffee, or tea, or a huge bottle of soda. Chug chug.
And yet for maximum efficiency, humans work best alternating between periods of high activity and periods of rest. We're not robots or computers, and we don't work like them. The most effective workplace would be one with periodic 20-minute naptimes. That mostly doesn't happen because it's a hard sell to the average manager.