In a previous brewpub I was at we made root beer.
250lb sugar in 10bbls, sodium benzoate, citric acid, salt and a gallon of Virginia dare root beer extract.
Boil it all sans the extract, pour the extract in the vessel and fill her up. Carb the thing for the whole weekend. Fresh stuff on Monday. Lasted about 2 months.
Had separate serving lines as the extract will leach into other lines unless it's the expensive aluminum foil Barrier line. The vessel for root beer could be hot caustic'd for days and all the rubber replaced and it still smelled like root beer.