A: They're all members of an extended family of fizzy, boozy lemonades. That is to say, Collinses and Fizzes are both sours (alcohol + citrus juice + a sweetener - read more about those here) with a good measure of club soda or seltzer added.
Tall, summery, and decidedly old-fashioned, this family of mixed drinks makes a light, thirst-quenching alternative to shorter, stronger fare.
But what's the difference? Why are some drinks Collinses and others Fizzes? I didn't know the answer to that question, so I turned to a reliable source: cocktail historian, David Wondrich. In his award-winning book IMBIBE!, he sums things up neatly:
"It ultimately comes down to what you do with the ice...A Fizz is shaken and strained, a Collins built in the glass over large, slow-melting cubes."
Not much of a difference, is it?
MEET THE COLLINSES
The more famous of the two Collinses, this simple mixed drink is made with gin, lemon juice, simple syrup (or sugar), and club soda, and is garnished with a maraschino cherry and/or an orange wheel. The drink is said to have been originally made with an old-time sweetened gin called Old Tom.
The John Collins is a Tom Collins made with bourbon instead of gin. It was originally said to have been made with geneva gin, but bourbon is a standard modern substitute.
The Gin Fizz is almost identical to the Tom Collins (gin, lemon juice, simple syrup or sugar, club soda), except that it's shaken (the soda's added afterwards) and served in a slightly smaller glass, and without the garnish - and usually without the ice. Here are a few variations:
Silver Fizz: add a small egg white
Golden Fizz: add a whole, beaten egg (some recipes use just the yolk)
Sloe Gin Fizz: use sloe gin (a gin made with sloe berries) as a base
Ramos Gin Fizz (pictured above): add egg white, lime juice, cream, and orange flower water (recipe here)
Violet Fizz (pic at top of the post): add crème de violette (and sometimes egg white and/or cream as well). This one's become a new summer favorite for me:
VIOLET FIZZ (adapted from Ted "Dr. Cocktail" Haigh)
makes one drink
Combine all ingredients (except club soda) in a cocktail shaker with ice. Shake and strain into a highball glass and top with club soda. (And yes, in the dog days of summer, I say add ice to this fizz.)
Related: All in the Cocktail Family: Sours
(Images: Nora Maynard)