Add peaches, rosemary, sugar, and water to a small saucepan over medium-high heat.

Bring to a boil for about 10 minutes and remove from heat. Cover and let steep till it cools down.

Strain and discard solids.

In a jug, add half of the syrup. Top with the soda and lots of ice.

Pour into glasses and garnish with rosemary sprigs and peach slices.