The gin sour is a classic cocktail made with gin, lemon juice, and sugar that predates Prohibition in the United States. Adding club soda water to the mix turns it into a gin fizz. The egg white is optional but adds a beautiful layer of foamy texture atop the drink, which you can then decorate with bitters. Usually 2-3 drops of Angostura bitters. This sour is light, refreshing, and with a lot of character, one of the original cocktails of its kind appreciated in a similar manner since the late 1800s.