Combine 300 g granulated sugar and 240 ml water in a small saucepan. Bring to a gentle simmer over medium heat, stirring until the sugar has fully dissolved. Do not boil vigorously. Once dissolved, remove from heat.

Add acidity and preserve

Stir in 30 ml fresh lime juice and 2 tsp citric acid (if using) into the hot syrup. This brightens the flavor and helps preserve the syrup. Allow the mixture to cool to warm (about 10–15 minutes).

Incorporate flavor

While the syrup is still warm, whisk in 60 ml of your chosen flavor concentrate/extract/puree (see Flavor Options). If using fresh fruit juice (e.g., mandarin, pineapple, grape), strain through a fine mesh to remove pulp for a smoother Jarritos-style soda. For tamarind, dissolve tamarind paste into a little warm water first to make a syrupy concentrate, then add. Taste and adjust: for a brighter lime-forward soda add up to an extra 15 ml lime juice; for sweeter fruit character add 1–2 tbs more sugar to the syrup before cooling.

Chill the syrup

Cover the prepared flavored syrup and refrigerate until fully chilled, at least 1 hour. Chilled syrup mixes better with cold carbonated water and preserves carbonation.

Assemble the Soda

Measure chilled carbonated water: chill 1000 ml of soda water until very cold.

Combine syrup and soda water: In a large pitcher, pour 60–100 ml of the flavored syrup into the bottom (use 60 ml for a lighter, more soda-like sweetness similar to Jarritos; use up to 100 ml for a sweeter, fruitier bottle). Slowly add 1000 ml chilled carbonated water while gently stirring once or twice to combine. Do not vigorously stir — you want to keep as much carbonation as possible.

Taste and adjust: Taste the finished soda. If it’s too weak, add up to another 15–30 ml syrup. If too sweet, dilute with more soda water. If lacking acidity, add a small splash (5–10 ml) of fresh lime juice.

Serve: Pour over ice if desired (ice will dilute the soda slightly). Garnish each glass with a lime wedge or mint sprig for lime or tropical flavors.

Store leftover syrup: Keep any leftover chilled flavored syrup in a sealed container in the refrigerator for up to 2 weeks. Mix fresh with chilled carbonated water as needed.