In a blender, puree the cherries until smooth. Stir in the Sugar Syrup and the cherry lambic beer. Pour the sorbet base into an ice cream maker and freeze according to the manufacturer's instructions.
Pack the sour-cherry lambic sorbet into a plastic container. Press a sheet of plastic wrap directly onto the surface of the sorbet and close the container with an airtight lid. Freeze until firm, 4 hours.