You're right smokey, it was the sugar. Anytime you are using a sugar or tomato based sauce, you should wait until the final 15 or 20 minutes before it is applied. You probably had the problem due to the high concentration of brown sugar in the sauce. Next time, do everything the same, except wait to add the finishing sauce until the end. You can go ahead and spray down the ribs using the apple cider several times throughout the cooking process to keep them moist. HTH.
No, it ain't burnt- it's barbecue