Cooking with sugar makes pan very difficult to clean
Melted and re-hardened sugar (including caramel) is very difficult to remove through mechanical action, but trivial to remove by soaking. Just pour in enough hot water to cover the sugar and wait an hour or so. (If oil was used, add some dish soap.) For a quicker turnaround, you can simmer the pot with the water on the stove; 10 minutes should be enough to remove even a thick coating.