I use leftover Starbucks from our morning pot of coffee, but omit the sugar and vanilla. Sometimes I purposely make extra coffee and store it in a covered pitcher in the refrigerator so we have plenty on hand to make this refreshing drink (especially during the hot summer months). Just a tip: If making this with cold coffee from the refrigerator, it is easier to stir the chocolate syrup into the milk and then add the coffee, than it is to stir it into the coffee first. You can easily adjust the amount of coffee to milk ratio to make it the strength you want. We think this tastes every bit as good as the iced coffee from Starbucks, and it can be made for a LOT less!