I would definitely recommend maybe chocolates and candies. Stuff like MnMs, Oreos, Nerds and so on. Crisps (or as Americans call them, chips) would also work quite well. I'd say Pringles or Walkers/Lays might do the trick. I also know there's Cheese Puffs and Space Invaders. Popcorn is also a pretty good snack to have about. Coke and Pepsi are musts I find, though if caffeine is allowed I'd imagine you could get away with Rockstar, Monster or Red Bull.