Whisk together the water, brown sugar, pumpkin purée, vanilla extract, and all the spices into a saucepan.
Bring to a simmer over medium heat. Then, reduce the heat to low and simmer for 3 minutes or until the sugar has dissolved and the syrup has slightly thickened. It's a simple syrup so it shouldn't be thick like caramel.
If desired, strain the mixture through a fine mesh strainer. This will remove the spices so if you're worried about the texture that the mixture of spices will leave, I recommend this step. I personally skip this step because it doesn't bother me.
Store in an airtight jar in the fridge for up to 2 weeks.