Skinnygirl® Sweet 'n Tart Grapefruit Margarita. Made with blue agave silver tequila with triple sec and natural flavors. Natural flavors. 9.95% ALC/VOL (19.9 proof). 750ml. Everyone loves flavored margaritas, but no one wants the guilt or the calories. That's why we created the Skinnygirl® sweet 'n tart grapefruit margarita. Made with natural flavors, blue agave silver tequila, and lightly sweetened with agave nectar. Skinnygirl® sweet 'n tart grapefruit margarita: the margarita you can trust. - Skinnygirl cocktails. (Per 1.5 fluid oz - average analysis: calories 37.2, carbohydrates 3g, protein 0g, fat 0g). skinnygirlcocktails.com.