I will always get flagged as Iowan because of the following word: pop.
It's falling out of favor a bit in the Midwest, but I refuse to stop calling it pop. "Soda" means "soda water."
Actual conversation I've had more than once.
Them: "I call it 'soda' because it's 'soda pop.'"
Me: "What do you expect to get when you order a 'vodka and soda' at a bar?"
Them: "...soda water."
Me: "EXACTLY MY POINT!"
Yes, I know in parts of the south all soda pop is called Coke, and I do think that's ridiculous because it is unclear! Pop makes more sense because it differentiates it from soda water.
@AllegraIntegra Do they call Sprite Coke? Because that would be clear and unclear at the same time.
Even more confusingly, I've been told that in a very small part of New England, soft drinks are referred to as "seltzer".
@peterdrake In parts of the South, yes, Sprite is "Coke." Coke is used as a catch all for any soft drink/soda pop.
Example:
"I'd like a coke, please!"
"What kind? We have Pepsi, Sprite, and A&W."