Apples can rot faster is they are bruised. This happens sometimes when they fall from the tree instead of being picked. Also apples can rot faster is they left in the heat too long. This speeds the decaying process. Other reasons that will cause rotting faster is if the apple has been sliced it is exposed to oxygen which breaks down the apple's core.
Sugar will speed up the decaying process of any organic material such as apples. Salt and vinegar will act as preservative. Apples rotting is a natural process. Generally speaking, the better the apples the faster they rot.