Just do it - have fun.

Peanut butter & jelly sandwiches tend to be easy to eat and still bike afterwards.

I usually carry a granola bar of some sort and some cliff shot bloks with caffeine.

Put a 2nd water bottle on your bike if you can - but if you're not going to be riding in the middle of nowhere, there is usually a store or someone's garden house or something that you can stop by and fill your water bottle up.