although it's reasonably common usage - in my part of NZ anyway - it stopped when I was about 10 or so and I spent the rest of my NZ life not using a generic term for soda. Then I moved to the US, and say soda.
Coke. Because it's usually Coca-Cola. Unless it's ginger ale. Then I call it "ginger ale."
I grew up in a "pop" area, moved to a "Coke" area, and now live in a "soda" area. But "soda" is just wrong, because that means soda water. And really, I prefer "soft drink," but that makes me sound like a fast-food menu writer. So the whole thing's fraught and due to the trauma, I just try to avoid all carbonated flavored beverages to the best of my ability.
Actually, what I'd like to call the fizzy beverage that's most often in my fridge is "frizzy water," but people look at me funny when I do so. But it's frizzante in Italian, and "frizzy" just seems more accurate than "fizzy" -- more jangly and mineraly, somehow.
I've lived most of my life in Chicago and thereabouts, but when I was a kid I apparently was a Southerner, because we called everything Coke. Mostly because that's what it was, usually -- except at my grandparents', where we mostly drank Dr. Pepper.
I say "pop". I am after all, Canadian. Funny story:
When I was in first year of uni a friend and took a road trip on my spring break. We were pretty broke, so short was good...we ended up traveling to Rochester NY, to visit the Great House of Guitars. On the way back, we figured we'd eat before we crossed the border, so stopped at a Pizza Hut. Before the waitress arrived, my friend Steve very carefully explained to me that in the states, they don't call it "pop", they call it "soda".
Cue the waitress, I ask for an iced tea, and Steve asks for a soda. His request elicited a very funny look on the waitress' face as she paused a beat, then asked, "And what KIND of soda would you like?". I bit my tongue until she walked away, Steve blushing like a madman, and then I thanked him for helping us blend in and not look like idiots.
none of the above. in rural southwestern Ohio where I spent most of my formative years you'd typically ask for an "RC", sometimes a "yoo-hoo". Kids who asked for the generic "pop" were weird suburbanites whom we typically viewed with disdain.
I've only heard the "What kind of Coke?" line used when someone was telling me that's how they do it in Texas. I've never actually heard it used sincerely (even in Texas, not that I've spent a ton of time there). I look forward to the day it finally happens to me.
Anyway, I grew up saying pop (my parents were from a pop region), but we eventually transitioned to soda and that's what I say now.
I see this repeated over and over, the notion that Coke is used throughout the South as a generic term for a carbonated beverage. This might be truer the farther one goes from the heart of Georgia, but Coca-Cola HQ is right here on North Avenue. One Coca-Cola Plaza.
In Atlanta, when we ask for a Coke, it'd better damned well be a Coca-Cola. A Coke is not a Pepsi. A Coke is not a root beer, a lemon-lime soda or a ginger ale. And while Atlantans might debate the merits of living inside the Perimeter* versus outside the Perimeter, we're all rather unified in our appreciation/recognition of the local soft drink of multi-national merit.
So much so that you can watch waiters tense up at restaurants that sell only Pepsico products.
Waiter: Can I get you started with some drinks?
Patron: Yeah, thanks, can I get a Coke, please?
Waiter [trying to hide a grimace, bracing himself]: Ah. Is Pepsi ... okay?
Patron [disappointed]: No. I'l just have a water ... unless you have sweet iced tea?
Waiter [dying inside]: Um. It's not sweetened ...
Patron [sighing]: That's okay.** Water'll be fine, I guess.
* - I-285, the by-pass than encircles metro Atlanta.
** - It's very much not okay, by the way.
I call it soda because i grew up in St. Louis. I live in Columbia, MO now, and there should be an all of the above color for places like this. I've literally heard every single one of these used in the last week. We are a melting pot inside a melting pot shrouded in a mystery and wrapped up in an enigma or maybe just a college town with an internationally renowned Journalism school.