Syrup is a thick, viscous liquid, containing a large amount of Inverted sugar syrup, also known as simple syrup, is a basic sugar-and-water syrup. It is used by bartenders as a sweetener to make cocktails, Inverted sugar syrup, also known as simple syrup, is a basic sugar-and-water syrup. It is used by bartenders as a sweetener to make cocktails,dissolved sugars, but showing little tendency to deposit crystals.