The foxtrot is a slight riff off the daiquiri with a slightly more lively color thanks to the addition of grenadine. Now, you would think grenadine is just for color, but a good quality grenadine (such as Jack Rudy Grenadine or Liber & Co) will give a slight tart flavor along with a little bit of sweet as well.
The sweetness of the grenadine along side the sweetness of simple syrup offsets the sour lime and creates a nice flavorful cocktail experience and thus, the Foxtrot is born.
2 oz. Bacardi Superier or other light rum, 1 oz. lime juice, 1/2 oz. simple syrup, 1/2 oz. grenadine.