Caramel-flavored coffee syrup can be found by the coffees and teas in the grocery store.
The caramel sauce can be made ahead. Store it covered in a microwavable bowl in the refrigerator until serving. Just before serving, uncover bowl and microwave on High for 2 minutes 30 seconds to 3 minutes 30 seconds, stirring occasionally, until the sauce comes to a full boil. Watch carefully so the sauce doesn’t boil over the edge of the bowl.