CLKD
There are some really lovely cordials, Bottle Green, that kind of thing. Elderflower, Pomegranate, Ginger cordial. Or you could get one of the water bottles that you can add fruit to in a little cage? I'm sure there's a scientific name but meno brain here can't think of it haha.
Also if you've got a supermarket near you, you could try some of the cold tea infusions, if tea is up your street?
I wish I could drink things like fruit juice or iced latte's, nothing is ever as easy when you are lactose intolerant. Fruit juice just kicks my reflux off. I would not be pleasant to sit next to