Mix milk, cream, pumpkin spice sauce, and vanilla syrup in a mason jar and shake to combine. Alternatively, you can stir all ingredients together in a bowl. If you're not using right away, keep in an airtight container in the fridge (you can use this pumpkin sweet cream in coffee as is if you want).
Turn mixture into cold foam right before using. You can either use an electric frother, hand mixer, or blender. Just add the sweet cream and froth, mix, or blend until the mixture turns into a foam. Alternatively, you can shake the mixture in a mason jar until it's frothy.
Pour cold foam over the drink of your choice and top with pumpkin pie spice if desired.