I'm no fan of our culture's mania with multi-tasking; I don't advocate replacing sleep with double and triple shots of espresso. Actually, if I don't get enough sleep, I'm prone to mini-seizures, in which I'm unable to speak for about fifteen or thirty seconds. (That's due to the scarring on my brain from the surgery I had over twelve years ago.)
Still, there's no beverage as enlightened, and enlightening, as tea for that kick of caffeine for a little boost. And of course, there's a world full of varieties without that particular chemical--and they're equally delightful!