I recently got a machine for adding bubbles to water. Cost me 10 € used, including an empty CO₂ bottle which I can change for a full one at any hypermarket by paying 7 € for the content (which enbubblifies a 1-litre bottle about 60 times, they promise).
And then I can mix that with some lemonade concentrate to get cola or sprite or orange lemonade or whatever. Or I can just put a lemon juice on the bottom of the glass, add a little bit more sugar than that amount, and then pour that water with bubbles atop it.

Works like charm and has the added bonus that I don't need to lug full bottles of lemonade in my backpack to my district that is located unfairly on top of a very mean hill. I can always make just the amount of lemonade I really want, and I can have one glass of this taste and one glass of that. Any juice concentrate works for adding the taste. I found orange juice concentrate that has simply "orange" as its ingredients and makes much tastier lemonade than anything I could buy from the shop.
Plus, the mark's own cola concentrate is tasty.

And obviously you can always just buy water with bubbles. But then you'll have to lug it around, which kind of meh. It weighs.