1. Combine water, sugar, fresh mint leaves, and lime zest in a small saucepan. Bring everything to a simmer over medium heat, stirring until the sugar completely dissolves. Once it starts simmering, remove from heat and let it steep for 10 to 15 minutes.

2. Pour the syrup through a fine mesh strainer into a bowl or jar. Press down on the mint leaves with the back of a spoon to squeeze out every bit of flavor. Let the syrup cool to room temperature.

3. In a large pitcher or 1-liter bottle, combine the fresh lime juice and cooled mint-lime syrup. Add cold water to fill the container, leaving a little room at the top. Shake or stir everything together and refrigerate until completely chilled.

4. When ready to serve, drop a few fresh mint leaves into each glass. Use a muddler or the back of a wooden spoon to gently press the mint leaves to release their oils.

5. Fill each glass with ice cubes, then pour in the chilled limeade base until the glass is about halfway to two-thirds full. Top off with chilled sparkling lime water for that refreshing fizz. Garnish with a sprig of mint or a lime slice and serve immediately.