Measure one quart (4 C) filtered water (NOT water kefir!) into a saucepan. Heat to a simmer while adding sarsaparilla, anise stars, cloves, and ginger.
Simmer gently, not allowing to boil, for about 45 minutes. Stir in sugar, molasses, and vanilla until they dissolve.
Cool completely, then strain the solids out and pour the remaining liquid into a bottle or jar for storage.
To make root beer water kefir, pour one quart of plain water kefir into a bottle and add half a cup or so of the root beer syrup. cover the bottle tightly and allow to ferment until it reaches the desired level of fermentation. "Burp" the bottle daily by removing the top to release pressure and prevent any explosion!
When the mixture is as bubbly as you want it to be, put it in the refrigerator. Serve very cold.