There are tons of Ruby Cocktail recipes floating around in cocktail land including, but not limited to:
1) a gin, grenadine and applejack recipe similar to the Prohibition era Pink Lady cocktail,
2) a rhubarb-infused vodka with simple syrup and fresh lime created by Vanessa Bortnick of Harry Denton's Starlight Room in San Francisco,
3) Tony Abou-Ganim's vodka, elderflower and Aperol version, and
4) The SATC Ruby.
The Sex and The City version of the Ruby Cocktail was created by the Florida Citrus Commission to boost sales of Florida grapefruit. To further encourage grapefruit sales the recipe was proposed to the creators of SATC as a replacement for the what had been the signature drink of Carrie, Samantha, Charlotte and Miranda, the Cosmopolitan. The producers liked the idea and the SATC Ruby made its debut in Season 4's Episode 12 "Just Say Yes". Eventually, the more widely recognized Cosmo made it back as the SATC signature drink in following episodes (as well as the first Sex And The City movie) and the Ruby went into the same sitcom oblivion as the flock of discarded SATC paramours.
It's really too bad The Ruby didn't stick around because I personally prefer the fresh ruby red grapefruit juice spiked with citrus vodka over the ubiquitous cranberry, vodka and lime Cosmopolitan.
6 Oz Fresh (Florida) Ruby Red Grapefruit Juice
3 Oz Citrus (Absolut Citron) Vodka
Garnish: Sugar Rim, Grapefruit Twist
Tools: Cocktail Shaker
Glass: Large (10 ounce) Martini/Cocktail
Shake ingredients with ice, strain into the sugar rimmed, chilled glass then garnish with a grapefruit twist and serve.