Anecdotally, I know that a mid-day soda seems to keep my prodcutivity higher - though if I drink too much, there's always risk of a crash. I had assumed it was the caffeine, though maybe the glucose plays a role as well. Anyone else have a similar experience?

ETA: I'll add that I've also long noticed that eating regular meals, especially relatively balanced and nutritious meals (relative to, say, an entire bag of potato chips), also seems to keep my productivity up.