There are waterless washes and rinseless washes. If you happen to be in a drought area and have a complete water ban on washing your car, you might be able to get away with a waterless wash. A waterless wash, as the name implies, uses a special detergent where you would put it in a foam dispenser and it sprays out as a foam then you wipe it off with MF towels. This typically takes less than 1L of water (about 0.4 gallon). There is do drips and leaves little to no traces of water use. Check out Ammo NYC's video about rinseless washing
Rinseless wash will use about 1-2 gallons of water. You would use a concentrated detergent like Optimum No Rinse and mix it in a 1-2 gallons of water. You follow the conventional style of 2 bucket method washing but instead of rinsing after wiping down a panel, you can just dry it with a towel immediately.