I mean you could even return the cup at the airport so if you forget to return it in town you could deposit it when you leave.
It’s just like bringing your own bags to the store, sorting your trash for recycling or returning bottles and cans to the store.
Just return the cup and get your deposit back.
It’s my fault isn’t it?
I am literally leaving for the UK in 12hrs in hope that the weather would be a bit warmer.