The op was more concerned with security issues about accepting a drink during a punt.
Indeed. But I think if he's big enough to punt he's big enough to decide if and when and how to accept a drink (or not). What's the worst that could happen? Robbed, wake up in the bath with lots of ice and a kidney missing, abducted by terrorist abolitionist pimps, or beaten up or knifed to death by a crackhead or psycho. The world is a scary place. But the chances of a good prossie doing that are pretty negligible.
When punting in a slightly dodgy (or unknown) strange country, or the same for an unknown situation, I extend my safety zone bit by bit. Start very careful indeed. Read the signs. Do that over a number of different punts while considering potential dangers. Think of every bad thing that could happen and how to deal with it / minimize it / avoid it. There's no one rule to fit every situation. You simply learn and grow safely and sensibly. Each time you find a similar situation you know more and extend your comfort zone a few more degrees. The fact that there are nutters out there gives pause for thought. Not paranoia.
If you want to be 100% safe it is better to stay in the care home or your parents' bedroom, hoping the roof doesn't cave in while you're asleep!