I read recently that honey, specifically the kind of sugar in it, worked as well as any commercial sport goo out there for providing calories during the ride. The honey-lemonade recipe I got from that site is easy:

1/2 cup honey
1/2 teaspoon lite salt (optional really)
1/4 cup lemon juice
7 1/2 cups water
That's only 3 water bottles worth, so multiply the recipe as needed.
(Dissolve honey in lukewarm water.)

150 calories per 20 oz. water bottle