It's one of those age old questions like what really killed the dinosaurs, what came first... the chicken or the egg, then is it "Pop" or "Soda". You're most likely going to hear "Pop" from the Yankees and Midwesterners. Southerners will correct those of you from North of the Mason Dixon Line and tell you it's "Soda". Y'all, when in the South you go by their sayings. Or just order beer because that's a universal term.