Look, we all do it.
For most SEC schools the preference is the ol' ziplock baggie or airplane bottles down the bootleg, but that's because they don't let you bring ANY of your own drinks into the stadium.
However, for venues like Turner Field where BARVES fans can bring their own drinks (as long as they aren't alcoholic in nature) this video might come in handy if you want to avoid looking and smelling like you've got a drank on you.
My assumption is that it also works for pre-mixing whiskey into a Coke bottle (for those of you like myself who avoid clear liquors...because we're men) but I found this to be a nice resource.
Of course you could just simply add it to an already opened Coke and try to walk in...but lets face it, whiskey has a unique smell. It looks a little suspicious if you stroll through a turnstile with a built-in smell of masculinity, freedom, and the ability to dance already on your person.
Just thought I'd share. I'm sure since this is the internet someone will just comment that I'm a retard and provide a much more simple (yet less inconspicuous than a factory-sealed bottle) method...but whatever.