I found this recipe on the internet:
3 oz brown rice syrup
1 1/2 oz honey
1/2 oz blackstrap molasses
1/4 teaspoon sea salt
My wife found the brown rice syrup at the health food aisle of our local grocery store, most health food stores should have it. Honey is honey. And I bought a big thing of molasses for $0.45.
A 5 ounce batch works out to about $2 (vs $5-10 for the equivalent gel packs!).
Brown rice syrup is the main ingredient in some of the commercial gels. According to the wikipedia entry, it's made up of:
50% soluble complex carbs
The molasses gives you potassium (about 100mg per ounce). I found the taste too strong to deal with, though, so I scaled it back and use sports drinks to get my potassium.
I've tried it a few times - it's not bad, cheap, and I don't notice any kind of difference in energy from commercial gels.