When doing long distance rides I find it easier if I put many of the calories into my water, I prefer maltodextrin mixed with a little bit of Gatorade. I can get 600+ calories in 24oz of water if I want to though I usually stick to 200-400 considering I drink about one bottle an hour here in the desert. I'll also take along a granola type bar for some real food. If I really think I'll need the calories I'll also take some homemade gu.