In a small saucepan, bring the water and sugar to a boil over medium-high heat, stirring constantly, until the sugar has dissolved, 2 to 3 minutes. Set aside to cool for 20 minutes.
In a blender, combine the cooled syrup, peaches, strawberries, lemon juice, and lemon zest. Blend until smooth. Add the sparkling water and pour into an ice-filled pitcher.