My current favorite recipe is modified from Jeffrey Morgenthaler. http://www.jeffreymorgenthaler.com/2008/how-to-make-your-own-tonic-water/
4 cups waterCombine ingredients in a medium saucepan and bring to a boil over high heat. Once mixture starts to boil, reduce heat to low, cover and simmer for 20 minutes.
1 cup chopped lemongrass (roughly one large stalk)
3/4 cup whole cinchona bark
zest and juice of 1 orange
zest and juice of 1 lemon
zest and juice of 1 lime
1 tsp whole allspice berries
¼ cup citric acid
pinch Kosher salt
Remove from heat and strain out solids using a strainer or chinois. You’ll need to fine-strain the mixture, as it still contains quite a bit of the cinchona bark. You can use a coffee filter and wait for an hour or more, or do as I do and run the whole mixture through a French coffee press.
Once you’re satisfied with the clarity of your mix, heat it back up on the stovetop or microwave, and then add ¾ cup of agave syrup to each cup of your hot mix. Stir until combined, and store in the attractive bottle of your choice.
Combine syrup to carbonated water, soda water often has too much sodium. I like to make virgin cocktails with the tonic water as it has an interesting flavor profile in itself, but do taste the magic of gin combined with this recipe. Cheers