A while ago I was absent-mindedly twiddling a cylindrical jar of sugar that I used to keep at work (for tea purposes) and I noticed that when I rolled the jar across my desk it would stop quite quickly due to the friction of the sugar against itself.
Then I got to wondering what would happen if you put the jar of sugar on some sort of spit or lathe like device that would keep it turning over (not so fast that the sugar would spin around with the jar) and if the jar was a good insulator. The energy put in as rotation would build up in the sugar, heating it up and (presumably) eventually turning it into caramel. Weird.