Add kumquats, sweetener, and 1/2 ounce gin (amount as original recipe is written // adjust if altering batch size) to a serving glass and muddle to break down sweetener and release citrus juices. Add remaining gin and stir well to combine.
Add ice and top off with sparkling water to achieve desired strength of drink. Add 2-3 ounces for a stronger drink and 3-5 ounces for a weaker drink (amounts as original recipe is written // adjust if altering batch size).
*If subbing lime for kumquats, add 1/2 lime, juiced, to the cocktail when sweetening. Then slice the other half for garnish.
*Nutrition information is a rough estimate for 1 Gin and Tonic with 1 Tbsp sweetener.