After three months of pretty much no caffeine (3 Cokes in 3 months), don't drink two Mountain Dew's after 5pm on a Sunday evening. Unless of course the goal is to lie awake until 2am. Then it's a great plan!
Side note: With only 4 (fairly lousy) hours of sleep, I'm surprised I'm as awake as I am. Two thirty this afternoon could bring a whole other story!