Just a question?

I have a very important question about soda. In American TV programmes people are always requesting/being offered something mysterious called ‘soda’ which as far as I’m aware is used as an umbrella term for ‘fizzy drink’ in the United States. So my question is: do people in the States not care what flavour their drink is? When someone orders soda in a restaurant, what do they get? Coke? Fanta? Lemonade? Or is this a Hollywood thing and people in real life are actually more specific?