Okay, I'm a bartender so I feel a professional obligation to weigh in on the BYO situation. Bringing outside booze to a bar isn't just a dick move/trashy/stealing from the establishment or server, it is also illegal. And in my state, the bartender is responsible for such things. If the liquor control board does a random inspection and finds that you have a flask or water bottle of cocktail or ANYTHING on you and I'm behind the bar, I get a very large fine and lose my mixologist permit, which means I LOSE MY JOB. So please don't fuck me over, alright? Keep your flask in your car and go take nips off it when you take a smoke break. I do, however, think it's perfectly acceptable to bring booze to venues that are not specifically alcohol-centered like sporting events, movie theatres, (some) concerts, zoos, street fairs, etc. I do it all the time!