Being a cheapskate, and disliking buying endless plastic bottles of drink, I looked into DIY rehydration drinks. A great simple one is:

1 part Orange Juice, or other juice of choice
3 parts water
good pinch of salt.

Not very pleasant unless you're thirsty, in which case it tastes great. Either way tastes better to me than Gatorade, and doesn't have scary dyes in it.

I'm sure there are some other electrolytes in the likes of Gatorade, but for potassium, you can always buy some of the "Lo Salt" salt alternative (potassium chloride, rather than sodium).