Slice the peaches in half and remove pits, then cut into thin wedges on a cutting board using a sharp knife.
Combine sliced peaches, sugar, water, and lemon juice in a medium saucepan. Turn on heat to medium and stir until sugar dissolves, bringing the mixture to a gentle simmer. Continue simmering for 10 minutes, stirring occasionally, until the peaches soften and the syrup slightly thickens.
Remove the saucepan from heat and strain the syrup through a fine strainer into a bowl, pressing gently on the peaches to extract maximum flavor. Discard the solids or reserve peaches for garnish.
Pour the warm syrup into glass bottles or jars and let it cool to room temperature. Refrigerate for at least 30 minutes to chill before serving.
For each drink, fill a glass with ice cubes if desired. Add 2-3 tablespoons of peach syrup and top off with fresh sparkling water. Stir gently to combine and garnish with extra peach slices for visual appeal.
