Run the lime wedge around the rims of two margarita glasses. Pour the sugar onto a small dish, and dip the glasses into the sugar. Set aside.
Fill a cocktail shaker with ice cubes. Pour in the sweet and sour mix, triple sec, tequila, raspberry liqueur, and simple syrup. Squeeze a few drops of lime juice into shaker. (Too much lime can make it taste bitter.) Cover and shake until the outside of the shaker has frosted over. Pour into the prepared margarita glasses.