Combine 2 cups granulated sugar and 1 cup water in a small saucepan. Add 2 tablespoons light corn syrup if using. Heat over medium, stirring until sugar fully dissolves and liquid is clear. Bring just to a gentle simmer for 2 minutes to ensure infusion, then remove from heat.

Flavoring

Infuse flavors

While the syrup is hot, add the chosen flavoring components: 3 tablespoons total of fresh citrus zest and/or juice (e.g., 1 tbsp lemon zest + 2 tbsp orange juice) or 3 tbsp of concentrated flavored extract (cola, orange, etc.). Add 1 tablespoon of optional aromatics (a split vanilla bean, a cinnamon stick, or 1 tablespoon sliced fresh ginger). Stir to combine.

Steep

Cover the pan and let the mixture steep for 20–30 minutes off the heat so the flavors infuse into the syrup.

Strain

Strain the syrup through a fine-mesh sieve or cheesecloth into a clean heatproof container to remove zest, spices and solids. Press solids to extract maximum flavor, then discard solids.

Acid and Balance

While the syrup is still warm (but not hot), stir in 2 tablespoons fresh lemon juice and 1 teaspoon citric acid if using. Taste and adjust: add more lemon juice for brightness or a pinch more citric acid for sharper tang. Let the syrup cool to room temperature.

Carbonation & Serving

Chill and mix

Chill chilled carbonated water and glasses. For a single serving (approx. 1 cup beverage): combine 2 to 3 tablespoons of the prepared syrup with 1 cup (240 ml) chilled carbonated water over ice in a glass. Stir gently to combine. Adjust syrup quantity to taste (start with 2 TBS for light sweetness, up to 3 TBS for fuller sweetness).

Alternative concentrated ratio (batch)

For batch mixing, a good starting ratio is 1 part syrup to 8 parts carbonated water by volume. For a 4-cup finished batch, mix 1/2 cup syrup with 4 cups carbonated water, taste and adjust.

Garnish and serve

Add ice as desired and garnish with lemon/lime wheel, fresh mint sprig, or a maraschino cherry. Serve immediately to preserve carbonation.