"Hold still, let me get you some water to wash out your mouth."
"I'm of a mind to wash your mouth out for the words you're thinking."
He excused himself, went to the men's room to wash out his mouth and take a look in the mirror.
I waited a minute, and then washed my mouth out again.
And a bucket of fresh water, so he can wash his mouth out.
Having your mouth washed out was never this much fun.
I washed out my mouth several times and then drank.
"Is that why you were so intent on washing my mouth out?"
"Here now, wash out your mouth and don't take it so hard."
If my grandson talked to me like that, I'd wash his mouth out.