I'm reading a book right now that...I guess it's set in Chicago, though the author never says exactly where the main character lives. And by "set in Chicago," I mean it takes place in the actual city, not the suburbs. This is somewhat important.
At one point in the book, the main character goes on a date, and the author describes a table in the pizzeria where said date takes place as being "sticky with soda."
Soda? What? No way. People from Chicago and Cook County (where I grew up) call that fizzy stuff that comes in cans "pop." Except for my mom. (Hi, Mom!) So I Googled the author and found that she's not from Cook County but Lake County, which according to the very highly scientific Illinois pop-vs-soda survey has a slightly higher incidence of calling that fizzy stuff that comes in cans "soda" than Cook County. Even more, people who live in Cook, Lake, and DuPage County have lower instances of calling it pop than the rest of northern Illinois. But the fact still stands: A narrator from Chicago is much more likely to call it "pop." My family has lived in Chicago and Cook County for generations and the only one of us who ever calls it "soda" is my mom. My friends and I at my Cook County high school? Called it "pop."
More stats on "pop" vs. "soda" vs. "Coke" can be seen here: Generic Names for Soft Drinks.
You'll notice, looking at the map, that all of New Jersey is olive green, meaning that 80-100% of the survey respondents refer to it as "soda." True story: For my very first Teen Advisory Board meeting in New Jersey, I said to the members, "I am happy to get you whatever kind of snacks you want, so if you have food allergies or if you like a certain kind of pop, please let me know."
They all looked at me as though I'd grown a second head and said, "It's SODA."
I never understood why anyone would call it "soda." It's called "pop" because that's what it does! Fight that logic, New Jersey.