So if you weight 140 pounds, an energy bar and a banana will give you exactly half the amount of post-ride carbohydrate you need. On long rides, especially in hot weather, you may need more fluid than you can carry in your bottle. Consider a back-mounted hydration system like a Camelbak. These clever backpacks let you carry up to 100 ounces of fluid in a plastic reservoir and sip it through a tube with a valve that releases fluid when you bite down on it. You don't have to take your hands off the handlebars or reach for a bottle.
Many models even have room for additional gear like rain jackets and energy bars.