I used Gu back when I rode endurance with my horses. Now I use Hammer Gel. The Apple Cinnamon is my favorite. The chocolate is good but a bit too thick for my tastes, it is almost like brownie batter. Ben uses that chocolate Hammer Gel. Each big container comes with a nifty little flask. That is handy.

Some endurance riders I know would use Eagle Brand milk. Yummy, but how useful is it? I don't know.