Most cocktails call for a teaspoon of sugar to sweeten the drink.
If you were to add granulated sugar, you'd have a gritty drink that promotes tooth decay. Sugar doesn't dissolve well in alcohol, nor in a chilled drink. To make your own simple syrup, dissolve two cups sugar in one cup water, until the water boils. The longer you boil the water, the stronger the syrup. Bottle your concoction in attractive container so it doesn't look so simple.