use to do this for kstate football games all the time, they never really patted down in security, unless ur wearing some huge winter coat. The best thing to do in my opinion is get like a 750 plastic bottle of your favorite liquor (say kentucky deluxe) best if its a plastic bottle. wear loose jeans put the bottle between your boxers and jeans, tighten the belt and have your shirt untucked, nobody will ever notice. Just go with a buddy, buy 2 big soda's pour out some soda and make some big strong mixed drinks.
on a side note i snuck like 6 beers when i was drunk into the kstate/colorado football game, needless to say i was hammered and whipped out a beer and started chugging it in the aisle. Kicked out of the stadium before the game even started.