For the fruit skewers: Arrange the pineapple, raspberries and tangerine segments on four 4 1/2-inch wooden skewers, alternating the fruit.
For the mimosas: To rim the glasses, pour 2 tablespoons of the grenadine in a small bowl. Pour an even layer of sanding sugar onto a small, flat plate. Dip the rim of a 6-ounce champagne flute into the grenadine to create a thin film on the rim. Then immediately dip it into the sanding sugar and give it a quick twist to make sure the rim is evenly coated. Repeat with 3 more champagne flutes.
To make the mimosas: Pour 1/4 cup of the pineapple-orange juice into each glass. Top with 3 ounces of champagne. Gently and slowly pour 2 tablespoons of grenadine into each glass. If you do this too quickly, you will lose the beautiful sunrise effect. Lay the fruit skewer across the top of each glass and serve.