I ran my first beer mile a few months back and managed a 7:30. I was aiming for sub-7:00, but it was a bit tougher than I thought. The chugging is the worst part, and I had trouble keeping it down on the last lap - which was pretty slow in the middle 200m. I was most impressed with a girl in our group that doesn't really run but was an impressive chugger. The chugging is what let her run in the 8:40s (a really good time for a girl).
You might want to head to a track and attempt to do a few quarters while using Coke to simulate the beer. This will give you a decent idea of what it's like to chug from a can after a lap and how to deal with the carbonation.