To make the simple syrup, add pumpkin puree, water, sugar and pumpkin pie spice to a small saucepan. Bring mixture to a boil over medium-high heat, stirring constantly. Once the syrup is boiling and smooth, remove from heat and cover. Let sit for 15 minutes.

Strain the pumpkin mixture into an airtight container. Let cool completely before making the cocktail. Syrup can be stored in the refrigerator for up to 1 week.

In a small bowl, stir together ingredients for the cinnamon rimming sugar.

Rub the edge of a rocks glass with a lemon wedge.

Pour the rimming sugar into a shallow dish. Rim the rocks glass with sugar. Set aside.

Fill a cocktail shaker with ice. Add pumpkin spice syrup, bourbon and lemon juice for the cocktail. Shake well.

Fill rimmed rocks glass with ice. Strain the cocktail into the glass.

Top with soda water. Give the cocktail one final stir and serve.