Add the chicken stock and apple cider vinegar to the Instant Pot insert.
Next, add the chicken thighs. Sprinkle over the garlic powder, paprika, and salt.
Finally, pour ¾ cup of BBQ Sauce over the chicken thighs. Do not stir.
Attach the lid and ensure the valve is in the “sealing position”. Set the timer for 15 minutes. When the timer finishes, allow the pressure to naturally release for 10 minutes. Then, quickly release any remaining pressure by switching the valve to the “venting” position.
Remove the chicken to a cutting board and shred it.
(Optional) If you like a thick sauce on your sandwich, turn the Instant Pot to the Saute-Normal function and whisk in 2 tablespoons of flour. Cook, stirring occasionally, for 2 to 3 minutes or until the sauce has thickened enough to coat the back of a spoon.
Return the chicken to the Instant Pot and add the remaining ¼ cup of BBQ Sauce.
Serve immediately. Store any leftover BBQ chicken in an airtight container in the fridge for up to three days.