Look, we’ve all done something stupid with a flask. I once filled a mouthwash bottle with vodka and offered "minty refreshment" to a police officer. He did not laugh. The lesson? Know your audience. And maybe don’t do that.
At the end of the day, the best way to sneak alcohol is to simply buy the ticket that comes with a complimentary bar. But if you can’t, remember: a little creativity, a lot of confidence, and a truly unreadable poker face are all you need. Just don’t blame me if you end up trying to explain why your sunscreen tastes like a cheap cabernet.