This is interesting. I say soda, but again I’ve lived in many states for several years each.
I just now had an interesting visit with my daughter from Kansas who lives in Idaho who had talked to a friend from upstate New York who said that one is supposed to say pop. (!) At my daughter’s objection, she responded that soda is baking soda. Proof? Go into the grocery store and ask a clerk where the soda is. They’ll take you to the baking soda aisle. Ask for the pop and they’ll take you to the pop section.
I’d not previously thought of that difference.
My Dad from Iowa would have known better. He always asked for soda pop.