Powdered Christophsian sugar donuts were doughnuts coated in powdered Christophsian sugar. They were served on the planet Coruscant in Dex's Diner where they were made by a Crisp-E-O donut droid in a traditional Adarian style every morning. They cost 1.5 credits.
Sources
Dining at Dex's on Hyperspace (article) (content removed from StarWars.com and unavailable)