Chevron Mesa Gas Station - 1143 N Ellsworth Rd, Mesa, AZ 85207 $15 or $10 with a gas or propane fill.

Some of the water stores will fill your rv for .25 a gallon. You just pull up to the front they have hoses. There is a water store on Main Street in Apache Junction. Otherwise fill your own 5 gal jugs at water station and pour or pump it in your rv.

Good Sam members can dump and get water for free at the Camping World in Mesa. They do check your membership. The basic annual membership is $29/year. They take 2 business days to process your membership. Don't do what I did and buy it the day you want to use it :) The KOA in Apache Junction allows you to purchase water/dump. I don't recommend it, but it'll do in a pinch. Their water is super slow. Water is $30 no matter how many gallons you get. Dump is also an additional $30. I saw people mentioning the Circle K in Apache Junction in posts down below. I do not recommend this. They were quite rude. I assume they've had enough of people asking them for free water, even though I asked if I could PAY for water.

Creativity RV did a nice episode on where to find water while boondocking: https://www.youtube.com/watch?v=1GaYDfuPlWQ

Apache Junction