Add the drained jackfruit, sliced onion, minced garlic, smoked paprika, cumin, salt, pepper, and 3/4 cup of the BBQ sauce to the slow cooker. Stir gently to coat the jackfruit evenly.
Cover and cook on low for 6 hours or on high for 3 hours until the jackfruit is very soft.
Use two forks to shred the jackfruit directly in the slow cooker. Stir in the remaining 1/4 cup BBQ sauce and let it warm for 10 more minutes.
While the jackfruit finishes, combine the shredded cabbage, shredded carrot, vegan mayonnaise, apple cider vinegar, maple syrup, salt, and pepper in a mixing bowl. Toss until the vegetables are lightly coated.
Spoon the pulled jackfruit onto the bottom halves of the sandwich buns. Top each with a generous scoop of slaw and close with the bun tops.