The difference, by the numbers
Both have lime juice and honey syrup. Only the Don’s Special Daiquiri has Jamaican rum, white rum and passion fruit syrup; only the Spicy Fifty has vanilla vodka, elderflower cordial and red chili pepper. In parts, a Don’s Special Daiquiri is 2 rum, 1 rum, 1 passion syrup, 1 lime and 1 honey; a Spicy Fifty is 5 vodka, 1½ elderflower, 1½ lime and 1 honey. By volume, the Don’s Special Daiquiri is 50% spirit, 33% syrup and sugar and 17% citrus; the Spicy Fifty is 55% spirit, 28% syrup and sugar and 17% citrus. That makes them close cousins on the ratio map.
They are about equally strong in the glass (both 12.5% ABV), and they hold about the same alcohol (1.01 and 0.99 standard drinks). The Don’s Special Daiquiri has more calories (about 172 against 149) and more sugar (18.0 g against 12.8 g). The Don’s Special Daiquiri is blended and served in a goblet; the Spicy Fifty is shaken and served in a coupe.