1. Take the baby back ribs. Remove the membrane by first cutting a portion with knife and using a paper towel, tearing it off. Place them in a large pot.
2. In a large bowl, mix cider vinegar and brown sugar.
3. Pour it over the ribs and let it sit for 2 hours.
4. Preheat the grill on high.
5. Preheat the oven to 250 degrees F.
6. In a small sprayer mix 1 part cider vinegar to 1 part brown sugar. Mix them well. Keep aside. It can be done in a bowl also.
7. Discard the marinade and place the ribs on the grill with the bone side up and sear them. Allow them to form a brown crust.
8. Then move them to the upper rack or on indirect heat on the grill and cook for 2 hours with the bone side down.
9. Baste the ribs with the vinegar and brown sugar mix one in a while by spraying on it or brush it on the ribs if sprayer is not available.
10. After 2 hours, take it out of the grill. Place them on a wide mouthed baking dish.
11. Brush half of them with the apple juice barbecue sauce generously.
12. Brush the other half with spicy mustard sauce generously.
13. Cover the baking dish with foil and bake them in the oven for 1 hour.
14. After 1 hour take them out, brush them again with the respective sauces, cover with the foil and continue baking for another hour.
15. Remove the foil off before the last 20 minutes to allow the sauces to caramelize.
16. Take it out of the oven and let it sit for few minutes.
17. Place them on the serving platter.
18. On a serving plate, slice and serve the ribs warm with vegetables and buttermilk biscuits.
If your grill does not have an upper rack, scoop the charcoal to one side of the grill and place the meat to cook over indirect heat.