I use Starbucks vanilla coffee syrup, but don’t worry if you don’t have any! To make a vanilla simple syrup, combine ½ cup of granulated sugar, ½ cup of water, and 1 vanilla bean (split in half lengthwise) in a small saucepan set over medium heat. Bring to a boil and cook until the sugar has dissolved. Then, set it aside to cool for 30 minutes. Remove the vanilla bean and store in an airtight container in the fridge for up to one week.