Empty entire bottle of barbecue sauce in the bottom of the Instant Pot. Place chicken on top of sauce. Add about a quarter cup of water to the now empty bottle of barbecue sauce, and shake to get any remaining sauce off the sides of the bottle. Pour over the chicken.
Dump entire can of pineapple, juice and all, over the chicken. Put the lid on the Instant Pot and cook on manual for 15 minutes, then use the quick release. Shred chicken with two forks, and leave in the sauce.
While chicken is cooking, cook the riced cauliflower in the microwave, then place in a bowl.
Dish up riced cauliflower into individual bowls and top with shredded chicken and pineapple, and desired toppings.
Store leftovers in an airtight container, in the refrigerator.