Sour mix

[1] It is made from approximately equal parts lemon and/or lime juice and simple syrup and shaken vigorously with ice.

This produces a pearly-white liquid with a pronounced flavor.

Optionally, egg whites may be added to make the liquid slightly foamy.

It may also be served neat or with juice, club soda, etc., as a soft drink.

These typically consist of a powder which must be rehydrated by adding water prior to use.