Place the chicken breasts in the bottom of your slow cooker.
Arrange the sliced onion and bell peppers over the chicken.
In a separate bowl, whisk together the enchilada sauce, taco seasoning, cumin, chili powder, and water.
Pour the sauce mixture evenly over the chicken and vegetables.
Cover the slow cooker and cook on LOW for 6 to 8 hours or on HIGH for 3 to 4 hours, until the chicken is cooked through and easily shreds.
Remove the chicken from the slow cooker and shred it using two forks. Return the shredded chicken to the slow cooker and stir to coat with the sauce and vegetables.
Serve the chicken and pepper mixture warm in tortillas with your preferred toppings.
Notes
For best flavor, use a low-sodium taco seasoning or make your own blend.
If you prefer a thicker sauce, remove the lid for the last 30 minutes of cooking time on HIGH.
This filling works well for meal prepping lunches for the week.