>talking about stuff that seems amazing to me but sends my friends to sleep

I've just looked at your profile, Bonzo - it looks like you are in the right place here.

I'm sure that we've been here before. In soft drink terms, my (UK) understanding is:
Pop - old fashioned word, used by my parents generation, anyone of my years would regard it as an insult - implying that the person asking thinks that we are about five.
Soda - The stuff that people used to put in whisky from a soda syphon (you can buy bottles of soda water now) http://www.kitsch.co.uk/babycham.htm. I never knew what a soda fountain was - I always imagined a kind of place that children could go with a fountain in the middle of the shop where you could hold out a glass and collect soda for free. I didn't like the stuff that I'd tried from a soda syphon so I couldn't imagine why anyone would want to go there. Similarly - "milk bar" - I wondered if they were places for people who didn't have fridges. Later, of course we got the "Sodastream" , a way of creating unrecognisable coloured fizzy drinks at a not particularly cheap price. Ice cream sodas were good though when you could get one (yes, MG, that must be the same as an ice cream float).
>coke - we are doing fizzy drinks here, aren't we? In that case it's a generic name for coke-like drinks. So you could ask for a coke in a bar and they would say "we only have Pepsi, is that OK?". Really sad generic coke-like drinks are called "cola" and tend to only have the required colour but no particular flavour.

As MG says, lemonade is a clear (or maybe yellow coloured) fizzy drink. It will only taste of lemons if it says "old fashioned lemonade" and then, probably not that much. Sometimes you will be offered "Sprite" if you ask for lemonade but it isn't really the same - too much of a lemon flavour. Flat lemonade is hard to come by, as is iced tea (although becoming easier to find). As for Irn Bru ....

[Edit - spooky simultaneous reply Shona - we must be soul mates!]