I thought coffee was an excuse for breaks. I drink when I'm bored or need a short break. I have never ever felt that a coffee can give me a kick not even when I had to drive for 2 days or learn for exams.
On the other hand if I find something really interesting and/or exciting it can keep me awake till morning and I can't wait to get it solved not needing any stimulant food or even going to the bathroom.