You could bring foods for the boondocking part of your trip that are non-perishables. As a backpacker and RV'er I always take freeze dried meals, MRE's and even some canned goods with me. You can have onboard water, though I would filter it before drinking it. You can either have a case of bottled water or a half dozen Nalgene bottles full of water in a cooler. And if you really want to rough it, you can use a water filter and filter water from streams and lakes. You can always boil water with the propane stove on your RV. Or you can bring a backpacking stove and small propane canister.
Once you experience roughing it, you will appreciate the luxury of a full hookup at a campground! Good luck.