Do you have a heart rate monitor? For me, I know I start to go downhill when I hit the 500 calorie mark. I've yet to find anything that doesn't sit well with me while riding, so I guess I'm fortunate. Love Shot Blocs, even the Jelly Belly sport beans give a little boost. On long (50+ mile) rides, a peanut butter sandwich works wonders. Don't worry about the Camelback, my brother wears his. I usually like to carry one bottle with water, and one with Gatorade. I find that after 20 miles I need to start replacing electrolytes. Anything shorter than that and I'm ok with just water. Of course, you don't want to wait until you're hungry or getting tired and cramping to eat. You'll have to learn at what time you have to ingest something to avoid getting to that point. It will take you some time to figure out what your body needs and when.