Simple syrup is the most basic sweetener a bar or pastry kitchen makes: nothing but sugar dissolved in water. Because the sugar is already in solution, it blends instantly into cold drinks, batters and glazes without the graininess of undissolved granules — which is why it is the default sweetener of the cocktail bar, the base of sorbets and granitas, and the brush-on syrup that moistens and sweetens sponge cakes.