Can't take the credit for this one - it's from a guy whose got a blog named "Yaniverse" but unfortunately he's apparently locked his blog to registered users only.
Ages ago I bookmarked a do-it-yourself recipe that he posted for a Gatorade/Energy Drink substitute. Thanks to the magic of the internet, even though my recipe link no longer worked, I was able to find it online in someone's Google notebook.
First I'll give you his recipe (makes roughly 2L) and then some brief comments:
2 Tea BagsI know, my first reaction was, "Isn't that just tea?", and frankly it is, but the thing is, you don't need to buy fancy calorie laden energy drinks to help with sports hydration just like you don't have to buy fancy energy bars either - a whole wheat tortilla, smeared with some peanut butter and wrapped around a banana's a cheap and delicious alternative to a Powerbar anyday.
6 level teaspoon sugar (24 grams)
A pinch of salt (0.5 grams)
2 oz lemon juice (about 55 grams)
30 oz boiling water
200 mg Sodium
60mg of Potassium (from the lemon juice)
Caffeine varies, est 100mg-200mg caffeine (depending on the tea used and infusion duration)
Lemon juice: $0.10
2 Tea Bags: $0.06
Sugar, Salt, water, etc: negligible
If I remember correctly from Yani's readers' comments (before he locked his blog), obviously the type of tea matters dramatically in regards to taste and according to Yani, you can double the lemon juice if you want. I would suspect that if it's not sweet enough, you can either increase the sugar or add some Splenda - if your activity is longer than 45 minutes straight it may be worth adding more sugar as your body will need the fuel.
Yani, if you're reading, I'd love to link and credit you more formally, but I couldn't figure out how to find you through Blogger.
Update: Thanks to eagle-eyed reader Robert who calculated that 0.5grams of salt would contain roughly 200mg of sodium. Have changed the above to reflect same.