The Tom Collins is made from gin, lemon juice, sugar syrup and carbonated water.
It is normally served in a tall Collins glass filled with ice and topped with sparkling water. The combination gives the drink a balance of spirit, acidity, sweetness and refreshing fizz.
The cocktail belongs to the Collins family, named for tall mixed drinks built around a base spirit, citrus, sweetener and carbonated water. The John Collins is closely related, but its traditional base is Old Tom gin’s later whiskey-associated variant in many historical accounts, while the Tom Collins became associated with London dry gin.
The name also inspired the 1874 “Tom Collins hoax,” in which people were told that a nonexistent man was insulting them in a nearby bar. That joke helped spread the cocktail’s name.