Frozen run is for outlanders. The best is Kutztown Birch Beer, as the label says, "Nix Besser" (Pa Dutch for none better)
I still chew on Birch bark, and birch oil is still used as flavoring, even for wintergreen.
There were a few places that sold Birch Beer by the keg that had a low alcohol content. The old Dutch men would serve it to kids at reunions and picnics years back.
Birch sap is still gathered and boiled down to syrup by a few old timers around here. The sap doesn't begin to flow until after maple is done.