If worst comes to worst and you don't have enough time (I would not try for the run all the way downtown), you can get your fix of Bavarian food and drink right at the airport. Hofbrauhaus has a restaurant in T2, and there is an Airbrau (local brewpub/restaurant) between T1 & T2, as well as in the T2 departure area past security.

Or get on the S-bahn to one of the nearby stations and hit a restaurant by the station. 4 hours to downtown is cutting it close, unless you can fast track through security on the way back. Security lines in T2 seem to move pretty quickly, but if your flight is US bound, you get the second security check as well by your gate. If you do decide to go for it, the S1 or S8 stops at all the downtown underground stops. Augustiner Brauhaus is right outside and in between the Marianplatz & Karlsplatz-Stacchus stops. They have good food and heavenly beer.