I'd say, "Marion, since you like jeans and tennis shoes so much, you can wear them for the rest of the day, and in your vehicle driving home" then leave him at the airport, and would cut him from the team.
This would deliver a message that would go much further than a $500 fine ever could.
We're in a such a terrible position attitude-wise that mere words aren't going to work. Minor monetary consequences won't work either. A bold consequence would jump start the culture change and let the team know Garrett is dead serious. Barber has done Garrett a favor. Show the team you mean business, Jason.