I have a collapsing rubber sink too. Also small collapsible table. If I want to wash dishes, I put table far enough away from truck I dont make mud if I spill, that depends on terrain. Then I put minimum hot water in, and NO SOAP. The largest water usage comes from trying to wash off soap! But soap doesn't sanitize, it only bonds oil and fat to water to clean off oil and fat.
1. Use a small plastic scraper to remove all food residue from plates and pans.
2. Scrub pans in hot water with this stainless chain scrubber, it removes all residue without holding it to get smelly
Cleaning Scrubber
https://a.co/d/8VKKp9U
3. Wipe any remaining oil residue off and sterilize at once with Bar-keepers non-rinse sterilizing wipes:
HandyClean Rinse Free Sanitizing Wipes, Surface Cleaner Wipes, 120 ct of 9.5 x 7 inches Sanitizing Wipes
https://a.co/d/5BSXFjV
Basically, don't use soap to cut oil and you reduce water use 90%.
Don't make foods that are oily greasy to clean. Basic camp cooking tips for easy cleanup:
1. #1 camp cleanup rule: don't serve messy sunny side up eggs EVER, always scramble or omelet!! Carry pre-mixed egges in a bottle to pour out and save cleanup.
2. I do mostly premade, prepackaged stews and meals in vacpack, so reheating in hot water is fast. I have cooking writeups here showing this, correct size meals and boiling water amount to achieve hot meals. 1 Gal wide mouth cooler, 2 meal bags, 1.5 L boiling water, eat meals from bags for zero cleanup. 1.5L water stays in 1 gal thermos for later cleanup or coffee etc.
3. Serve tortillas to use for holding messy foods and wiping plates clean.
4. Serve oatmeal in large sierra style cups, easy to clean... and if they want coffee or cocoa after oatmeal, they have to clean out their own cup!! This works like a charm to get kids to clean own dishes.
5. Make most food and calories clean items. Nuts, trailmix, tortillas, meatsticks, sausages, whole fruits, handheld veg like carrots, celery, Broccoli. If cooked, make one-pot type meals that can be eaten from bowl. I do mostly chinese type dishes all fried in one 12" wok.