Study at night when you are awake anyway. Ask your teachers if they will allow you to make up any work that you are missing....then do it at night when you are awake anyway.

When I am sleepy in class, I pinch myself to stay awake. I've gone home from a class with deep red marks on the insides of my arms....but it seems to work. Also - drink lots of water. Dehydration will make you tired.

Best wishes - and sweet dreams....