In a small saucepan, combine the sweetened condensed milk, pumpkin puree, water, brown sugar, pumpkin pie spice, cinnamon, and salt.

Set the pan over medium-low heat and whisk constantly until the mixture is smooth and the sugar has dissolved.

Bring the syrup to a gentle simmer, then reduce the heat to low and cook for 4 to 6 minutes, stirring often, until slightly thickened.

Remove the saucepan from the heat and stir in the vanilla extract.

Let the syrup cool for 10 to 15 minutes, then transfer it to a clean jar or bottle.

Use immediately, or refrigerate once fully cooled. Shake or stir before each use.