Shake, strain, ice-filled highball glass. Top with soda and garnish.
Cointreau promotes this recipe as a riff on the Paloma (a Mexican cocktail traditionally made with Tequila, lime and grapefruit soda). This recipe seems to have been concocted by Cointreau's own mixologists and served at Cointreau's promotional parties since about 2012.
Ford Mixology Lab: http://fordmixologylab.com/2013/01/01/an-evening-at-la-maison-cointreau/