Knowing what will be available at the rest stops will help with your preparation. Usually there will be fruits;
bananas, oranges, etc. Bars from sponsors; Cliff, Kind, etc. But bring some of your own food/snacks if you
have a sensitive stomach. During training you'll get an idea what works for you; gels, hydration tabs, bars,
cheeseburger, etc. How much food and liquid intake will also be formulated. Prepare for the weather; if you
train/ride in all kinds of conditions(hot sunny, rainy, windy) - that will get you ready. Bring a spare tube, some
tools, a pump. Have fun; good luck.
I've volunteered as a marshal for most of the charity events in my area; always a lot of fun: