ok if you want to study long hours but can't, don't force yourself. you won't be very efficient at it. study for 45 minutes then rest for 15 minutes, then have another go at it again. your brain will be fresher and more susceptible to accepting information.

if you just want to do homework/assignment all night, drinking anything will help you along, inclusive of plain water. or else, just wash your hands everytime you're sleepy.