I've just had a Big Mac combo with my friend who is working on his study for tomorrow's test. (its 3:00am now)
we are in clubroom located in my college dormitory building, studying all day long....
Ra-myun(not sure for the spelling) is certainly a good midnight snack, but my whole face is often swelling right after that night.
So, not having any foods would be the best, but it's safe to say that some fruits such as apple or pear are the best choice for midnight snack.
Considering your health, that should come on the first.