You can read more about making tonic water in this post.
Home Made Raspberry Tonic Water
Zest only of ½ orange, 2 lemons and 1 lime (use a vegetable peeler)
20g citric acid
10g cinchona bark
¼ teasp Maldon sea salt
1 teasp lightly crushed coriander seeds
50g lightly crushed raspberries
Put everything into a jar. Shake well and leave in the fridge for 3 days, shaking every day.
Make a simple syrup by adding 250g sugar to 250g of water in a saucepan. Stir to dissolve the sugar, bring to the boil and remove from the heat. Leave to cool.
Tke the jar from the fridge, strain the contents through your finest sieve (I use a coffee sieve) and throw away the bits.
Now strain the liquid through a coffee filter paper, which is a bit of a pain but it will give you a bright and clear liquid. I find it easiest to do this in two batches, replacing the filter paper after the first batch. Using cinchona bark and not powder makes this easier.
Mix with the cold syrup and bottle.
Keep in the fridge and dilute 1 part tonic syrup to 4 parts still or sparkling water. Don’t shake as you don’t want to drink the sediment.