On the ISS each astronaut gets a packaged wet towel every two days, two dry towels and two washcloths a week, and 3 small packets of moist napkins every two days with which to wash themselves. At the end of the week these towels are discarded because there is no way to wash them. On earlier, shorter ISS missions the method was mostly to use wet wipes.
The method currently used also includes using a pouch of special no rinse body bath fluid that comes in pouches. (Or perhaps the fluid is sent in a bulk pouch and astronauts dispense it into the smaller pouches.)
Altogether this is a fair amount of mass and volume taken up on cargo missions so that astronauts can bathe. Could this be more optimal? The towels are standard terry cloth and the pouches are the same ones used for most fluids on the ISS.