I don't use sports drinks EVER.
I have heard of people making their own sports drinks. I think it is something like sugar, the no sodium salt substitute and lemon juice. You can not use normal table salt because any significant amount of sodium in the drink makes it taste nasty or so I understand.
But given the fact that you can buy gatoraide mix inexpensively, why bother with your own concoction? Doing it yourself would probably be more expensive.