Add sugar and water to a heavy-bottom sauce pan over medium heat. Stir gently until the sugar dissolves.
Stop stirring and bring the mixture to a boil. Allow it to boil for 7-8 minutes without stirring it; it should reach 250℉ on a candy thermometer and will be orange-gold in color.
Add butter. Whisk it in until fully combined, but be careful not to splash it.
Very slowly pour in the heavy cream, being careful as it may bubble up. Stir until fully combined.
Add pumpkin spice, cinnamon, and vanilla. Allow the mixture to boil for another 3-5 minutes until it thickens and is glossy. It should be a deep golden-brown color.