Hm. I drink coffee.
Or, if it's too late in the day, at least some hot tea. I can usually stay alert as long as I'm imbibing something, but I try not to snack as that leads to other problems! Otherwise, beats me. I get ridiculously dozy the minute I hit lecture class - it's because I'm not involved, I'm sitting quietly, still, being talked at (she's a really boring lecturer), etc. I'd be fine if I could move or type or something.