SLOW COOKER: Place the chicken breasts, 1/2 cup barbecue sauce, and water together in a slow cooker. Cook on high for 3-4 hours or until chicken can be easily shredded into the sauce. Drain excess liquid from chicken (reserve). Shred chicken and return to slow cooker. Stir in additional 1/2 cup barbecue sauce. Add reserved barbecue sauce/water to moisten the chicken if necessary. Keep warm until ready to serve.
INSTANT POT: Place the chicken breasts, 1/2 cup barbecue sauce, and water together in an Instant Pot. Cook at high pressure for 8 minutes (make sure valve release is sealed). Do a quick release and make sure chicken is cooked through and shreds easily. If not, repeat the steps but cook for only 2 additional minutes. Drain excess liquid from chicken (reserve). Shred chicken and return to Instant Pot. Stir in additional 1/2 cup barbecue sauce. Add reserved barbecue sauce/water to moisten the chicken if necessary. Keep warm until ready to serve.
STOVE TOP: Place the chicken breasts in a sauce pan or pot and cover with water. Bring to a boil, and then reduce heat to a simmer for approximately 20 minutes. Once chicken can easily be shredded, remove it from the pan. Shred the chicken, return it to the pan, and stir in about 1/2 cup of barbecue sauce and 1/8 cup of water. You can add more barbecue sauce and/or water if you prefer. Cook on medium heat until the sauce is warmed.
For the Jicama Apple Slaw (prepare at least 2 hours before serving)
Peel and julienne the jicama and apple (you can use a food processor). The julienned shreds of jicama and apple should be about the size of a matchstick.
Stir the lime juice, olive oil, salt, jalapeño, cilantro, and mandarin oranges together in a bowl. Toss in the jicama and apple. Cover.
Refrigerate until serving.
Putting it all together
Prepare each pita by opening the pocket. If necessary, use a thin, sharp knife to cut it open without tearing the sides.
Fill the bottom half of each pita with the BBQ shredded chicken and the top half with the jicama apple slaw.