Powdered sugar is used more as a natural mite control, although you would usually dust the entire hive.
I feed them with sugar water, the water goes where the hole is, I put some powdered sugar in as I was refilling the sugar water.
It looks like they enjoy eating the powdered sugar, the bonus seems more that it is keeping them occupied. They are typically not happy about having the top of their hive opened up.
I thought it was interesting how for the most part they all just line up around the edge.
RE: Bees like powdered sugar