From It Flows:
2 oz. watermelon vodka
1/2 oz. tonic syrup
1 oz. watermelon puree
build over ice and top with soda water. Turn it over into a metal shaker and then serve in your favorite rocks glass.
Tonic Recipe #5
4 cups water
3 cups unrefined pure cane sugar
6 tablespoons powdered citric acid
3 tablespoons quinine (cinchona bark)
3 limes
3 stalks of lemongrass (chopped)
1/2 cup juniper berries
“Boil the sugar and water to dissolve, making a syrup, reduce heat
zest the limes in to the syrup
squeeze the limes and add the juice to the syrup
add the lemongrass
grind up the juniper berries and add
add the acid and the quinine, stir and then turn up the heat and bring it all to a rolling boil and then reduce heat and simmer for about half an hour.
Then I’ll strain the mixture into a large jar to get out the large particles. Put the jar in the fridge overnight and then gently pour off the syrup. The mass of quinine should sit pretty solidly in the bottom of the jar. There you have it. Just combine about 2 oz. of gin with 1 oz. of syrup over ice, squeeze in a fresh lime wedge and top with soda.
I have done many variations on this recipe, some work, some don’t. You can add other spices to create different tonics that work well with other liquors.”