Wiktionary
soapless
a. Without soap.
Usage examples of "soapless".
I took a scalding bath, soapless, squeezing the water from my skin, standing in the dark, fanning dry.
Rolling fish in bread crumbs before frying is also on the index, as is rinsing the dishes in boiling, soapless water.
He scraped the uneaten food from his plate, then swilled the plate and his knife and fork in the tub of soapless cold water that was provided for them to wash their dinner-things in.
It would have accumulated gradually over the weeks and months, and the occasional soapless baths he had managed would not have kept it down.