Taco Bell Cantina
2000 Guadalupe St, Austin, TX 78705
It's a concept so obvious, it's amazing it took this long to actually start doing it. Since no one goes to Taco Bell at 1 AM sober anyways, why not make it so you can get a little drunk AT Taco Bell? A lot more of these have been popping up all over, so this will lose the "new and interesting" feel soon, but until then, here you go!
And for the record, even though you would probably only expect cheap water beer from a fast food restaurant, this place does have a few local brew options. The one that comes to mind is Live Oak. A major concern for some of the beer snobs I know.