In a small saucepan, combine the water and sugar and heat gently over medium heat, stirring just until the sugar fully dissolves. Do not boil or reduce. Remove from heat immediately, add the lime peel and thin jalapeño slices, cover, and let steep for 10–15 minutes until lightly aromatic and subtly warm. Strain through a fine sieve and let the syrup cool completely before using.

Add the peeled cucumber pieces to a high-speed blender with ½ cup cold water. Blend until fully smooth and juicy. If the mixture struggles to move, add additional cold water 1 tablespoon at a time — the goal is flow, not dilution. Strain through a fine-mesh sieve or cheesecloth into a pitcher to achieve a clean, watery texture. Press gently but do not force pulp through.

Add 60 ml of the cooled syrup to the cucumber juice and stir gently. Add fresh lime juice gradually, tasting after each addition. The drink should taste crisp, cooling, and lightly structured with gentle citrus tension — never sweet or sharp. Adjust syrup or lime in small increments only.

Fill glasses generously with ice. Pour the agua fresca over the ice and garnish with long cucumber ribbons and optional fresh mint leaves. Serve immediately while fully cold and aromatically fresh.