Place the chicken breast, tomato puree, half of the apple cider vinegar, garlic powder, onion powder, smoked paprika, sea salt, and black pepper into a slow cooker.
Cover and cook on low for 6 hours or high for 3 hours until the chicken is tender enough to shred easily with a fork.
Remove the chicken from the slow cooker, shred it thoroughly using two forks, and then return it to the pot to toss with the remaining cooking liquid.
In a small mixing bowl, whisk together the remaining apple cider vinegar, olive oil, and honey to create a light dressing.
Finely shred the green cabbage and toss it with the dressing until well coated.
Split the sprouted grain bun and toast it lightly until the edges are golden brown.
Place the shredded chicken onto the bottom half of the bun, top with a generous portion of the cabbage slaw, and finish with the top bun.