If it's a morning ride over 25 miles either a bowl of oatmeal or cereal, or toast w/ butter or peanut butter, a banana, and a glass of water or two (or five depending on the previous night's activities). If I go for OJ my body starts hating me around mile 10, and there's no worse taste than citrus mid-ride. Any other time of day and it depends when I last ate, but usually no more than a PB sandwich or crackers/hummus with a piece of fruit.
If it's under 25 miles.. screw it, burn off the tank and start fresh afterwards.