Prep the slow cooker: Lightly spray the crock with nonstick spray for easy cleanup. Add the diced onion and garlic to the bottom.
Mix the sauce: In a bowl, whisk together Sweet Baby Rays BBQ sauce, salsa, taco seasoning, chicken broth, and lime juice.
Taste and adjust for heat by using spicier salsa or adding a pinch of cayenne.
Add the chicken: Place chicken breasts or thighs on top of the onions. Pour the sauce mixture over the chicken, turning once to coat.
Slow cook: Cover and cook on Low for 4–6 hours or High for 2.5–3.5 hours, until the chicken is fork-tender and easily shreds.
Shred the chicken: Remove chicken to a cutting board and shred with two forks. Return the shredded chicken to the slow cooker and stir to soak up the sauce.
Adjust the sauce: If the mixture is too thick, add a splash of broth.
If it’s too thin, let it cook uncovered on High for 10–15 minutes to thicken.
Warm the tortillas: Heat tortillas in a dry skillet or wrap in foil and warm in a low oven. Warm tortillas make better tacos.
Assemble and serve: Spoon chicken into tortillas and top with your favorites—cilantro, onion, cheese, jalapeños, avocado, and a squeeze of lime.