
If sours are the venerable ancestors of cocktails, then their "fizz" variants are the younger, cooler successors. A sour turns into a fizz by the mere addition of an acidic agent (such as lemon juice) and carbonated water. And as the name suggests, a fizz version of a cocktail is frothy and effervescent. In other words, fizzy.
Now we know we said the fizz was the younger, cooler descendant of the sour, but truth be told, it isn't all that young. There are mentions of it in reputed cocktail guides as far back as the late 1800s, and from the 1900s on, this class of drinks experiences a surge in popularity.
The Ginn Fizz is among the most famous of the fizz-es. Sort of like, if all the fizz cocktails were considered the Bennet sisters, then the Classic Gin Fizz would be Elizabeth.
Now you'll note that we use the adjective "classic" here. What's that all about?
The Gin Fizz itself has further variations. Depending on what is added to it — egg white, egg yolk, a whole egg, sparkling wine or crème de menthe — the "Classic" would be replaced by Silver, Golden, Royal, Diamond (also called 'French 75') or Green Fizz.
That's not all. There are other iconic iterations of the Gin Fizz Cocktail that have evolved over time beyond these five standard ones. For instance, you may have heard of the New Orleans Fizz/Ramos Gin Fizz, which makes use of gin, lemon juice, lime juice, egg white, sugar, cream, orange flower water and soda water. Or you might have encountered in the wild the Purple/Sloe Gin Fizz. Named for the sloe gin with which it made (a blackthorn plum flavoured spirit), this cocktail also incorporates grapefruit juice, simple syrup and carbonated water. An egg white is optional.
Coming back to the Classic Gin Fizz Cocktail, tradition decrees the use of four ingredients: gin (duh!), lemon juice, a sweetener of choice, and soda water. It is served in a highball or Collins glass to contain all of its foamy, frothy awesomeness (but this is not a must).
Note: If you're making one of the Gin Fizz variants that use egg white, the cocktail should be shaken without ice for the best results.