Neither fixes drowsy driving, but coffee and energy drinks buy similar alertness before you stop and nap.
A four-second lapse at highway speed carries a car over 100 yards, so NHTSA treats caffeine as a brief assist, not a cure. Both drinks work the same way: caffeine dose keeps you awake, not the label. Coffee is easier to dose because its strength is predictable; energy drinks vary widely and sometimes add other stimulants. Below: the milligram numbers, NHTSA’s stop-and-nap routine, and the mistake that sends drowsy drivers back on the road falsely recovered.
Caffeine Content Per Serving
Per 12 fl oz, the FDA lists brewed coffee at 113–247 mg and energy drinks at 41–246 mg. That overlap is the story: strong coffee can beat a mild energy drink, and a big can can out-caffeine a small cup. Mayo Clinic values per 8 fl oz: brewed coffee 96 mg, instant 62 mg, espresso (1 oz) 63 mg, energy drink 79 mg. An energy shot (2 oz) runs about 200 mg.
For driving, that spread matters more than drink type. The FDA considers up to 400 mg daily safe for most healthy adults—a ceiling, not a pre-drive target. Serving sizes are the trap: one bottle may hold two or three servings, understating what you swallow.
| Drink (Amount) | Caffeine | Notes For Driving |
|---|---|---|
| Brewed coffee (8 fl oz) | 96 mg | Most predictable dose; NHTSA names coffee in its stop-and-nap routine. |
| Instant coffee (8 fl oz) | 62 mg | Weaker per cup; a second cup may be needed to match brewed. |
| Espresso (1 fl oz) | 63 mg | Small volume, fast to drink, easy to overdo in a short stop. |
| Energy drink (8 fl oz) | 79 mg | Caffeine varies by brand; check the label, not the can size. |
| Energy drink (12 fl oz, FDA range) | 41–246 mg | Widest swing of any option, mild to very strong. |
| Energy shot (2 fl oz) | 200 mg | Concentrated hit; adds quickly to your daily total. |
| Brewed coffee (12 fl oz, FDA range) | 113–247 mg | Can exceed a standard energy drink depending on brew strength. |
Does Caffeine Keep Drowsy Drivers Safe?
Caffeine briefly improves alertness, but NHTSA warns it may not prevent microsleeps in a seriously sleep-deprived driver: you feel sharper while your brain still drops out for four or five seconds. It did not show energy drinks beating coffee, and its authors still stressed caffeine does not replace sleep.
NHTSA’s short-term procedure: drink one to two cups of coffee, pull over somewhere safe and well lit such as a designated rest stop, and take a 20-minute nap. That lifts alertness only briefly. If caffeine pills, pre-workout, or medication are already in your system, add them to the total before a second cup.
Which Should You Grab Before A Long Drive?
For an already tired driver, neither is reliably better; pick based on how well you know the dose. Coffee wins on predictability, which is why NHTSA’s procedure names it. Energy drinks are fine when you read the label and count every serving; their extra stimulants can sharpen caffeine’s effects, making jitters and a racing heart more likely. If you feel drowsy, caffeine is a bridge to the next rest stop, never permission to push through. Pregnant readers, people on interacting medications, and anyone with a heart condition should get medical advice first;
To compare specific cans and shots before your next trip, this roundup of energy drinks for staying awake while driving breaks down options by caffeine per serving. Whatever you choose, plan the nap stop before you turn the key, since NHTSA’s guidance on drowsy driving is clear that sleep, not stimulation, is the fix.
Common Questions
How much caffeine is too much in one day?
The FDA says most healthy adults can take up to 400 mg daily without generally negative effects; That’s a ceiling, not a target for a drive. Watch serving counts: one bottle may contain several servings.
Can I drink a second energy drink instead of stopping?
No. NHTSA warns caffeine may not prevent microsleeps in a seriously sleep-deprived person, so stacking drinks keeps you feeling awake without guaranteeing you stay that way. The supported routine is one to two cups of coffee, then a safe stop for a 20-minute nap.
Do energy drinks have more caffeine than coffee?
Not reliably. Per 12 fl oz, the FDA lists coffee at 113–247 mg and energy drinks at 41–246 mg, so ranges overlap heavily. Mayo Clinic puts an 8-ounce energy drink near 79 mg, close to a standard cup of brewed coffee.
Sources
- National Highway Traffic Safety Administration. “Drowsy Driving.” Source for the coffee-plus-nap routine and the microsleep warning.
- U.S. Food and Drug Administration. “Spilling the Beans: How Much Caffeine Is Too Much?” Source for caffeine ranges, the 400 mg daily reference, and the 1,200 mg toxicity estimate.
- Mayo Clinic. “Caffeine: How Much Is Too Much?” Source for per-8-ounce caffeine reference values.