There are two sizes of single-serving sodas sold commercially in the US.
A small one, a can, is 12 oz, 355 mL.
A large one is 20 oz, 591 mL.
To buy a 32-ounce soda, you'd have to do something very strange.
(There is another common commercial size, the two liter bottle of exactly 2000 mL. Those aren't intended to be bought and drunk; they're intended to be bought, taken home, and stored in your refrigerator over time.)
The largest coke you can order at McDonald's in the US is 380 calories (100g sugar) (not sure what size because it's not obvious from their website).
The largest coke you can order at McDonald's in Portugal (where I happen to be) is 197 calories (49g sugar).
- https://www.mcdonalds.com/us/en-us/product/coca-cola-large.h...
- https://www.mcdonalds.pt/produtos/mcmenu/bebidas/coca-cola-5...
https://en.wikipedia.org/wiki/Big_Gulp
At least they eventually reduced the Double Gulp down to 1.5L.
You might be able to do it at a 7-11, since they sell empty cups that you're meant to fill with a slurpee. I don't know if they also have soda fountains to fill those cups.