Problem: I keep falling asleep at my desk.

Solution: Replace your desk chair with a balance ball. 

I ordered my balance ball, which cost about $20, from Amazon.  Here's the link: Reebok Balance Ball

The ball inflates using a pump (included with mine), so you can deflate it when you move out of your apartment.  No more falling alseep at my desk, plus I can do core exercises while I study.  So, no more excuses not to work out.  This one came with a DVD which shows a 40-minute and a 20-minute workout using the ball.