On the food front - make sure that you're drinking and eating during the ride. Don't wait until you're hungry or thirsty, just take in a little liquid and food, and do it often.

Something else to practice is drinking while you're riding - either from one of your water bottles, or from a hydration pack like a CamelBak. That's a good thing to feel confident you can handle before you're out riding with a bunch of strangers!