On my rides last summer, I learned 2 -24oz bottles filled with straight water lasted me 25 miles. Anything longer than that and I was looking for a place to refill. As for food, I generally didn't carry anything but an emergency granola bar for a rare time I didn't eat enough before riding (never did eat it, still sitting in my handlebar bag where it'll probably be still waiting for me next season). Even on my 50-miler I did in July, I didn't bring any food.. I had my Camelback filled with water, one 24-oz bottle filled with water and the other bottle filled with diluted low-cal Gatorade. I did stop half way for a cheeseburger from a local restaurant though. As long as there's a chance you're riding through commercial areas, I don't see the need to bring any food.