Frankfurt is not known for beer, it is near wine country, and has cider. The local cider is tart, but goes well with the local food dishes. Sachsenhausen is the area just south of the Main river where you find a large concentration of the Apfelwein bars. There was Zwölf Apostel, but it is not a destination. In Mainz there was Eisgrub, all the beers had an off flavor.
If you have a full day and time is not a problem you could take a train to Bamberg, or up to Köln or Duesseldorf. Those are about 2 hours one way. Those are better beer cities.