Combine 1 cup granulated sugar and 1 cup water in a small saucepan. Warm over medium heat, stirring until the sugar completely dissolves. Do not boil vigorously. Once clear and dissolved, remove from heat and let cool to room temperature. Transfer to a clean jar and refrigerate. Yields about 1 1/2 cups; use 2 Tbsp per soda serving.

Prepare Flavoring

Prepare fruit purée or juice

If using fresh fruit, pulse 1/4 to 1/3 cup chopped fruit in a blender or food processor until smooth, then strain through a fine sieve to remove seeds and pulp for a clear soda. Measure 2 Tbsp of the resulting purée/juice for one serving.

Muddle herbs or ginger (optional)

If using mint or basil, place 4 leaves in the bottom of a glass and gently clap or press with a muddler or back of a spoon 2–3 times to release aromatic oils. If using ginger, grate a small thumb-sized piece and press to extract about 1–2 tsp of juice or steep thin slices briefly in hot water and cool; discard solids.

Assemble Soda

Fill a tall glass with about 1 cup of ice.

Add 2 tablespoons fruit purée/juice (or 2 dashes of concentrated flavor syrup), 2 tablespoons simple syrup, and 1 teaspoon fresh citrus juice into the glass. If using bitters, add 2 dashes now. Stir gently to combine the sweetener and flavors with the citrus.

Pour 2 cups (about 480 ml) cold carbonated water over the mixture. Pour slowly to preserve carbonation and reduce foaming.

Give the drink a gentle stir once to integrate the flavors without flattening the soda.

Taste and adjust: add up to 1 additional tablespoon simple syrup for more sweetness, or another 1/2 tsp citrus juice for brightness.

Garnish with a citrus wheel and a sprig of fresh herb. Serve immediately with a straw or stirring spoon.