
Pumpkin spice syrup is a flavoring syrup of sugar and water with the warm "pumpkin pie" spice blend.
Sugar and the dry blend are separable, which is why this is one of the easiest syrups to make rather than buy. A darker syrup carrying the same spice gets close and brings its own sweetness with it.
Pumpkin pie spice (dry spice blend)
The dry ground blend is what flavors the syrup — it brings aroma and no sugar or volume. Use it in place of the syrup and the drink loses its sweetness and its body, so add plain syrup to make both up.
Ground spice settles and the syrup separates, so shake before pouring. Refrigerated it holds three to four weeks; the spice note actually rounds out over the first few days before it starts to dull. Homemade with fresh purée keeps a week less.