1, I walk around the house to keep myself awake 2, I mostly study subjects with calculations during night cuz i will get sleepy with subjects that needs memorization and concentration so I read those after being sure that I am fully awake. 3, Try to write notes cuz it keeps you focused not only that but after reading try to write it in your own words without referring to your books so you will be focused on what you will write than your sleep and it will help you activate your memorization than before. Studying at night is really helpful if you use it to your advantage.