Building on what KimNTerry said, it depends on how close you are to your weight limits. My problem isn't the GVWR of the truck, it's my hitch weight limit. My fresh water tank is in front of the axles and 300# plus would put me way over my rated hitch weight. But I boondock almost exclusively. SO, I put 12 gallons in the fresh water tank and open a hot water faucet to fill the hot water tank behind the axles. 6 gallons in front of the axles and 6 gallons behind balance each other out. Then I fill four 6 gallon water containers which conveniently fit in the dinette bench storage right over the axles. I now have 36 gallons of water, about 2/3 my tank capacity and four containers to get more and haven't added any weight to my hitch.
Aside from the usual water sources on the road I've found Tractor Supply will let me use their outside hose if I'm buying something (propane). I've also been able to have one or two containers filled at McDonalds free of charge when I bought something.
2015 Bullet 220RBI
2019 Chevy Colorado extended cab V6 3.6 liter