I would never ever never pay $2.50 for a 20 oz. bottle of anything! Yikes!
That said, I would rather drink bottled than fountain. Especially in a bar, where most of them don’t actually serve Coke or Pepsi, but rather “cola” which tastes vaguely like both.
But in the situation above, there is no way I would pay that much for a bottle of anything that did not contain alcohol. I would instead get my pizza to go and buy my own soda at the store on my way home.