Depending how cold the cooler is kept (45-50[sup]o[/sup] F?), it’s not a good idea to drink much alkeehol; you’ll feel really warm at first, then your body heat will be gone and you could go hypothermic.
If you truly can’t get out, I’d say yes you need to stay hydrated and maintain your glucose levels. But then you have to get rid of it. What did he do, pee on the floor?
And most medical experts agree that high octane alcoholic beverages are the ideal avenue for this. Especially if you’re going to be trapped for an extremely long time like the 6 hours that guy claimed he was. 