Syrup keeps up to 2 weeks in a sealed jar in the fridge, or freeze it in an ice cube tray for up to 3 months and thaw overnight in the fridge. For a dairy-free version, use barista blend oat milk in the foam. For a hot pumpkin spice latte, warm 1 cup of milk and stir in 2 tablespoons of syrup. Don't stir the foam in immediately — the contrast between cold foam and coffee is the point. Start with 1 1/2 tablespoons of syrup and add more only after tasting.