In a measuring cup, whisk together vinegar, juice, olive oil, sugar, salt, and pepper. Place chicken in Crockpot and pour vinegar mixture over chicken. Cover and cook on LOW for 6 hours.
Shred chicken with forks and then add cumin, chili powder, garlic powder, and cilantro (if using). Cover slow cooker and let the meat rest for 10 minutes, and then serve with hard tacos shells, flour tortillas, or corn tortillas and the toppings of your choice.
Video
Notes
This recipe can be doubled and even tripled if your slow cooker can handle it. If tripling the recipe, increase the cooking time by 30 minutes. If you're doubling the recipe, there's no need to increase the cooking time.
The nutrition information calculated below is just for the shredded chicken. It does not include tacho shells and toppings.