The books say the Sutlers sold watered down whiskey at the big rendezvous. Of course if you had drunk nothing but water the previous 11-2/3 months then watered whiskey would be plenty good enough. There was sugar for sale at Rendezous and probably some hard candy and I assume some spices so some assembled drinks similar to Apple Pie may have been available, but I have never seen anything in writing. There are some old drink recipes that warrant exploring. I don't doubt that someone with an eye to profit was providing high priced drinks, but I haven't seen that in the books. That could have just been called watering the whiskey.
Many Klatch