True. Usually, for me, it's a stimulant to help me stay up. And that's usually on the night before tests/exams (yeah, not a good idea. But if it's on a subject you're not good at, it helps a little bit)
There is that 8-hour energy drink they advertise on TV sometimes that's not supposed to have any caffeine or give you that "hang over" but I haven't tried it yet.