Place the ribs to a large glass or ceramic baking dish and pour 2 cups of Coca-Cola or Dr. Pepper over them. Reserve the third cup of the soda for a sauce to be made later. Cover the pan securely with plastic wrap and let the ribs marinate in the fridge overnight.
Pour the remaining 1 cup of soda into a blender or food processor and add the ketchup, brown sugar, chili powder, pepper, dry mustard, and cinnamon. Blend until smooth.
Put the ribs in a roasting pan that has been coated with cooking spray, brush liberally with part of the sauce, cover the pan with a lid or foil and roast in a 225 F oven for about 2 1/2 hours or until very tender. (Can be done the day before. )
To finish, grill the ribs over high heat, basting with some of the leftover sauce until the outside is crispy, about 10-15 minutes. While the ribs are cooking, simmer the remaining sauce for about 20 minutes until a little thick.