Nuun tablets are brilliant. They taste a bit like Refreshers but as a drink and really hit the spot (a great hangover cure too).
I've tried a few things, Frij is too gloopy for me, it made me feel sick.
Yop is great, I can neck half a litre of that and feel fine, although why it's sold with a pop off lid in the UK and a screw top lid in France.
Dilute coke, well I've drunk it, but I'm not a fan.
Lucozade sport is OK, easily available, but too sweet.
Milk, makes my mouth fill up with spit - I can't explain it better than that really!
Natural fruit juices, too acidic.
Water, I can't absorb plain water, so combine it with crisps or salted cashew nuts.