1. To prepare the marinade, add the pop, barbecue sauce, brown sugar, chipotles, mustard, vinegar and garlic to a medium saucepan. Bring to a gentle boil and cook until reduced and thick, about 20 minutes. Allow to cool completely. Divide into 2 containers and refrigerate one container for later.
2. Brush the remaining container of the marinade all over the ribs on both sides. Wrap each strip of ribs individually in foil and refrigerate for 8 hours to marinate.
3. When you're ready to cook the ribs, preheat the oven to 135°C.
4. Place the ribs, still covered in foil, onto baking sheets and cook for 2 hours. Increase the temperature to 150°C. Open the foil packages and use the other container of marinade to brush another generous layer all over the ribs. Return the ribs to the oven with their foil packages still open and continue cooking for another 30 to 40 minutes, brushing on another layer of marinade as they cook.
5. Remove the ribs when they're fork-tender (keep cooking until they are). Slice and serve!