Put some piping gel on the side of the cake. Then fill your hand with the sanding sugar and press it onto the cake.
I asked this exact questions about a year ago, and was given the same exact answer, worked great. I also tried putting the sugar on a piece of card stock and holding it up to the cake, but you have to be very quick or it all runs down.
How do you attach the ribbon like the one in the photo you posted?
I'm wondering if using water-thinned Karo syrup would work if you didn't have any piping gel?
do you thin the pipping gel with anything or use it straight from the container?
does it affect the taste of the fondant?
Heres a recipe for those who want to try Piping gel (but dont have it on hand) (this will last in the refrigerator for up to 2 months) :
PIPING GEL RECIPE:
2 envelopes (2 tablespoons) Knox unflavored gelatin
2 tablespoons cold water
2 cups light Karo syrup
1. Sprinkle the gelatin over the cold water in a small saucepan and let set for about 5 minutes. Heat on low until the gelatin has become clear/dissolved - DO NOT BOIL.
2. Add the syrup and heat thoroughly.
tips: you can flavor piping gel with lorann oils. Piping gel can also be colored with your gel/paste colors.
If you dont have (or cant get) the unflavored gelatin heres a different recipe:
I use corn syrup to attach sugar crystals to fondant.....works great.