Dog Tired

I'm very tired today. I stayed up till around 5 a.m. chatting with a friend who was spending the night. I had a 9:30 a.m. Political Science I'm surprised I even made with a little pep in my step. However I've been at work since 11 a.m. and I'm exhausted. Any suggestions on how I can stay awake? I would have asked earlier but I was taking a nap on my desk.