Plan to consume approx. 250 calories per hour. Those calories can come from your sports drink of choice and/or your solid food.
Eat what you crave ... if you're craving that bag of potato chips, go for it. You likely need the salt. If you crave that cinnamon bun, go for it, you likely need the carbs.
Here, have a look around this site ... especially at the Nutrition articles:
http://www.ultracycling.com/