In a small saucepan, combine sugar and 1 cup water. Heat over medium heat, stirring until sugar fully dissolves. Remove from heat—this is your simple syrup.

In a blender, puree the sliced peaches until smooth (about 30 seconds).

Stir the peach puree into the warm simple syrup until well combined—let cool to room temperature.

In a large pitcher, combine the peach syrup, fresh lemon juice, and 4 cups cold water. Stir well.

Taste and adjust sweetness or tartness by adding more sugar, lemon juice, or water as needed.

Chill in the refrigerator for at least 30 minutes.

Serve over ice and garnish with peach slices, lemon wedges, or mint sprigs if desired.