Frost the rim of each glass by moistening it with an orange slice, then pressing it into the sugar and salt mixture.
Fill each glass with ice cubes. Pour the tequila, Grand Marnier and fruit juices into a cocktail shaker. Fill the shaker with ice cubes and shake vigorously for 10 seconds, then strain into the glasses. Decorate each glass with a pineapple wedge and an orange rind spiral.