I've seen these reusable cups at festivals: https://www.ecocupshop.co.uk/en/ https://www.ecocupshop.co.uk/en/ There's a 1€ deposit but some people keep the cup

I've seen these reusable cups at festivals: https://www.ecocupshop.co.uk/en/ https://www.ecocupshop.co.uk/en/ There's a 1€ deposit but some people keep the cup as a memento. Another side effect is thieves breaking into the festival tent at night to steal the plastic pipes containing dirty cups (so they can get the deposit for them).