How to make your own home made tonic water. Basically Jeffrey Morgenthaler's recipe, only Instructables style! http://www.jeffreymorgenthaler.com/2008/how-to-make-your-own-tonic-water/

Step 1: Recipe and First Steps

Here's the recipe:
4 cups water
1 cup chopped lemongrass (about 2 stalks for me)
1/4 cup powdered cinchona bark
zest and juice of 1 orange
zest and juice of 1 lemon
zest and juice of 1 lime
1 tsp cardamom bits
1/4 cup citric acid
1/4 tsp pink hawaiian salt

First I zested the citrus fruits, using a microplane grater.

Step 2: Add the Ingredients

Next, juice the fruits and chop the lemongrass.

Measure and add the cardamom, salt, citric acid and cinchona bark.

I got my cinchona bark from Tensing Momo: http://tenzingmomo.com/Qstore/p000429.htm

Step 3: Boil It!

Add 4 cups of water to the ingredients in a 2-quart or so saucepan and get it on the stove.
Once it starts to boil reduce the heat and simmer for 20 minutes.

Step 4: Strain It!

Once it has boiled for 20 minutes, pour it through a filter into a heat proof container.
I used a funnel with a basket lined with cheesecloth inside it. I then waited a bit and poured the whole mess through a coffee filter into my final container. Others have said this takes forever, but maybe I had a hole in my filter or something. It was fairly quick.

Step 5: Sugar. You Wants It.

So, what you've made at this point is a bitter, fragrant concentrate. My kitchen still smells awesome BTW. But! You want tonic water, which while bitter is still drinkable because of sugar.

So, I made some simple syrup: 1 cup sugar to 1 cup water, boil and cool.

You'll want about 1:1 syrup:tonic concentrate. Jeffrey suggests agave syrup; too rich for my blood but maybe I'll try it sometime. I got a lot of bitter stuff to mix!

Step 6: Make a Drink!

So, tonic water is a fizzy clear beverage. What is this concentrate stuff and how do I make a G&T out of it?

1 tablespoon concentrate, 1 tablespoon syrup, fizzy water to taste.

I make my own fizzy water nowadays, after following this excellent instructable:

https://www.instructables.com/id/DIY-Soda-Water-%26-Home-Carbonation---Pays-For-Itsel/

For a Gin and Tonic: as above, with gin (to taste!) and a slice of lime. Heaven!

Cheers!