Combine all ingredients except the sugar in a saucepan and bring to a boil for about 20 minutes. Let cool before filtering. Remove the large chunks, then filter out the cinchona bark however you can (see text).
Return filtrate to saucepan and add 4 cups of sugar (or to taste) and possibly another 1/2 cup of water. Bring to a boil until the sugar dissolves. Cool before serving.
To serve, combine in a rocks glass 1 shot tonic syrup, 1 shot gin or what-have-you. Top with about 3 oz soda water. Serve with lime.