I know it's stupid, but down here people say "coke" a lot of the time. I know, I know, it makes no sense at all, I don't know how it started. When someone asks you "do you want a coke?" the response is "what kind?". Really weird. But when I'm ordering at a restaurant I either say something like "I'll have a large drink" or the actual name of the drink. I rarely hear soda.