If I'm sleepy but have to study, I'll walk up and down, from my
living room to my kitchen, memorising things, repeating
them...
I find it very useful to read up, understand, memorise the points,
then pretend that you're teaching a class and spill out everything
you've learnt because if you can do that, it means that you have a
good grasp and understanding of the subject matter already.

And oh, I love a cuppa Hot Chocolate from 7-Eleven's at my
workplace when I'm on night duty... always perks me up! 