In a small saucepan combine 1 cup granulated sugar, 1/2 cup fresh orange juice, and the finely grated orange zest. Add 1/4 cup water. Warm over medium heat, stirring occasionally until the sugar fully dissolves and the mixture barely simmers (do not boil vigorously) — about 4–6 minutes. Remove from heat and let steep for 10 minutes to extract more orange flavor.

Strain the syrup through a fine mesh sieve into a bowl, pressing on zest to extract liquid. Discard solids. While still warm, whisk in 1 teaspoon orange extract, 1 teaspoon citric acid, 1 tablespoon fresh lemon juice, and a pinch of salt until fully dissolved. Taste and adjust: add up to 1/4 teaspoon more citric acid or 1/2 tablespoon more lemon juice if you want brighter acidity.

Let the syrup cool to room temperature. You can refrigerate for 10–15 minutes to speed cooling. The syrup will keep in a sealed container in the refrigerator for up to 5 days.

Assembling the Fanta Orange

Chill 4 cups of carbonated water (or chilled soda water/seltzer). Use very cold water for best fizz retention.

Add 3/4 cup of the prepared orange syrup to a large pitcher. This ratio yields a bright, sweet soda comparable to commercial Fanta; adjust to taste (use 1/2 cup for lighter sweetness or up to 1 cup for stronger orange flavor).

Slowly pour the 4 cups of cold carbonated water into the pitcher over the back of a spoon or down the side to preserve fizz. Stir gently once or twice to mix — avoid vigorous stirring.

Taste and adjust: if too sweet, add 1–2 tablespoons more carbonated water; if too tart, add up to 2 tablespoons more syrup or a pinch of sugar.

Serve

Fill 4 serving glasses with about 1/2 cup ice each (adjust to glass size). Pour the soda into glasses, distributing evenly.

Garnish each glass with an orange slice and an optional mint leaf. Serve immediately so the soda retains maximum carbonation.

Leftover soda: store in a sealed bottle in the refrigerator and consume within 24–48 hours; expect some loss of carbonation.