I’m not so sure that EU bar laws are similar to American laws as far as liability is concerned. But even if they are, there no reason that an establishment’s liabity would excuse the patron’s fiscal responsibility. He ordered the drink, he’s responsible for paying for it. Just because the customer decides he’s done drinking, I don’t see why then the bar owes him his money back. And there’s no law that says that drink has to be drank. Just put the drink down and go home.