One night earlier this week I told my kids they needed to hit the showers before bed time for sure. When they groused about it I reminded them they had been in intramural basketball games and had gotten sweaty.
Upon further reluctance from them I termed it this way:
'YOU smell like the inside of a hyena's butthole. And YOU smell like a steaming pile of vulture barf.'
Because when you are telling children to clean themselves up you really must reference carrion-eaters.
They didn't really smell bad but y'know, whatever it takes to get the point across.