a fling
A fling is when you ditch your husband at the bar to go bang a guy you just met. Then you come back, still drunk, and act like nothing happened.
I left my husband at the bar to go have a fling with the bartender.
She ditched her husband for a fling and came back with a hangover.
He left his wife at the club for a fling, and now he’s got a sore neck from laughing at her.