Slow Cooker Dr. Pepper Shredded Chicken

~3 pounds chicken breast (boneless, skinless)

Dr. Pepper soda (2 cans)

apple cider vinegar

tomato paste

roasted garlic

chipotle chiles in adobo sauce (plus ~1 tablespoon of the adobo sauce), more or less to taste

box Pomi crushed tomatoes

kosher or sea salt

freshly ground black pepper

tostada shells or warmed corn tortillas

fresh cilantro

thinly sliced red onions (or quick pickled red onions)

Mexican crema

crumbled Queso Fresco