It's a good idea to carry a few in your car for when you're feeling too sleepy but have to drive. It kind of wakes you up. Bad for students though. I used to take caffeine tablets when I had to stay awake all night and study for an exam (yes, I'm the biggest procrastinator in the galaxy). It keeps your eyes open but makes it very hard to concentrate. Advisable only as a last gasp hope of survival.