DirectionsCombine 2 quarts water, sassafras, sarsaparilla, birch, mint, star anise, ginger, and vanilla in a medium saucepan. Bring to a boil, reduce to a simmer, and cook for 10 minutes. Remove pot from heat, cover, and let steep for 2 hours.
Strain liquid through fine mesh strainer lined with cheesecloth into large pot. Add remaining 2 quarts water along with the brown sugar and molasses. Stir until mixture is integrated, then cover.
Let cool to 75°F, then stir in yeast and let it sit for 15 minutes. Fill plastic bottles with mixture, leaving 2 inches of space at top. Screw on caps. Keep bottles at room temperature for 36 hours, then open a bottle slowly and carefully to see if it is carbonated enough. If it is, then go on to step 4. If not, reseal the bottle and let rest for another 12 to 24 hours until desired carbonation is reached.