Wash the lemons well under cool running water. Pat them dry with a clean towel. Zest one lemon lightly, avoiding the bitter white layer underneath.

Cut the lemons in half and squeeze them using a citrus juicer. Remove seeds carefully. Strain the juice if you prefer a very smooth drink.

Add sugar and one cup of water to a small saucepan. Warm the mixture over low heat. Stir gently until the sugar completely dissolves.

Remove the saucepan from the heat. Let the syrup cool completely before mixing it with lemon juice. A cool syrup keeps the drink fresh and properly chilled.

Pour fresh lemon juice into a large jug. Add the cooled syrup and lemon zest. Stir everything together until the flavors are evenly combined.

Pour the remaining cold water into the jug. Stir slowly with a long spoon. Taste the mixture and adjust the sweetness if needed.

Add the cold sparkling water just before serving. Stir gently to protect the bubbles. This gives the drink a light and refreshing finish.

Place the jug inside the refrigerator for at least one hour. Chilling allows the lemon flavor to become smoother and more balanced.

Fill each serving glass with ice cubes. Add a thin lemon slice and a few fresh mint leaves. This makes the drink look fresh and inviting.

Pour the chilled lemon drink carefully into each glass. Serve immediately while it is cold and bubbly. Add another lemon slice for a beautiful finishing touch.