As others have stated, we wash dishes using a shallow bucket in the sink, and dump that water into the toilet. Doing this also helps when you dump the black tank - the soapy water helps thing flow.
"Navy" showers - a general term for showering using as little water as possible. Turn on the shower and get wet, then shut off shower. Soap/shampoo yourself. Turn on shower, rinse off as quickly as possible, then shut off shower. When you get used to doing this, you may surprise yourself at how little water you can use when getting clean.
