The sour is the fundamental cocktail template — a base spirit balanced with citrus (usually lemon or lime) and a sweetener (simple syrup, honey, or liqueur). These variations span classic and modern sours, from the Whiskey Sour, Amaretto Sour and Pisco Sour to the Clover Club and Sidecar, often finished with egg white or aquafaba for a rich, foamy texture.
