Call it "soda" (ugh) or "pop" (bigger ugh) in these parts and everyone will know you ain't from 'round here and may not be be trustworthy.
It's:
-- a soft drink,
-- Coke (if we mean Co'Cola, we'll say Co'Cola), or simply
-- "somethin' t' drink"
Oh, and CrimsonTide4 and enigma_AKA, y'all'll note that at least half of the blue/pop states are the ones with 1/2 person per every square mile.