From Daddy: Awwwwww.
“Hey, that’s cool!” he exclaimed from the bathroom.
He explained that when one puts soap in a cup of water, it can be used to wash hands as an alternative to the faucet.
“Yeah,” I said, “but what happens when you need your cup for drinking?”
“Ohhhhhhhhh,” he said with realization. He walked out of the bathroom with his soapy cup, put his cup on the kitchen counter, and returned to the bathroom with a clean cup.