Food wise, that depends on what I'm craving and for the most part, believe it or not, it's water because other drinks are cool and whatnot, but water hydrates and well, I need to be hydrated in the parks!
Caffeine! Anything w/ caffeine! But, when it's hot, I do drink water, but a good Coke now and then is great! Too much sugar makes me sleepy. Iced coffee! Iced Tea ( but not nestea!).