Before a double century I have a standard breakfast of a carton of yogurt, a couple of Pop-Tarts and a banana. Plus, I'll start the ride with Perpetuem in one of my bottles, so there's some nutrition from that early in the ride too.
Then I just eat a little real food at each checkpoint and keep refilling the one bottle with Perpetuem (Hammer products are available on most California doubles) and leaving the other with water, ice water on hot days.
Rick / OCRR