For a cocktail to share with your friends, peel 1 grapefruit, take the flesh and dice it up. Pour 1/2 liter of lemonade into a large serving bowl, add 8 ounces of rum, 15 gently crushed mint leaves, 2 tablespoons brown sugar and the juice of 2 limes. Add the diced grapefruit. Don't forget to garnish with a slice of lemon or grapefruit.