Tonic water is a carbonated drink, which contains quinine (obtained from the bark of the cinchona tree). Quinine gives tonic water its distinct bitter taste. Modern tonics contain considerably less quinine now, and often contain sweetners and other flavours.
Below we have selected a number of tonics, and other mixers which you can use to make a "Gin & Tonic" to your own taste. If you are not a fan of the bitter tonic taste (This was what originally got me drinking Gin! Gary @ GF), try a ginger ale for a warming hit of ginger, or a lemonade for a sweeter taste.
Remember - the mixer can considerably change the taste of your gin (cocktail, or other spirit). So mix and match and find the combination that works best for you!