I use a Camelbak so I can constantly sip water - just using bottles doesn't work well for me. I go through at least a bottle worth of water an hour; usually more. I use Hammer Endurolytes to get the electrolytes; 1 capsule every 15 minutes or so. For calories, I use gel mixed into one of my water bottles. I calculate how long I'll be out, then add enough gel so the one bottle covers the timeframe. For a longer ride that needs protein, I'll either eat a bar, or stop and get something. Just got some protein powder recommended by a nutritionist friend, and I plan on seeing how adding that to the gel mix will work for longer rides. That and the gel might make an interesting concoction... :-/

Hammer has some write-ups on their version of what is needed for rides of various lengths - don't know how valid their science is, since they are obviously pushing product. But there seems to be a rough consensus in the cycling community that over 2 hours requires some protein; less and you only need carbs. There is a limit on how many calories you can process per hour, so taking in more than that won't help your ride performance.