To reheat instant pot mac and cheese, scoop out whatever portion size you prefer into a bowl and add a splash of milk. Place in the microwave for 1 minute. Remove and stir together. Place back into the microwave for a couple of minutes or until hot. Add more milk if needed to reach the desired consistency. As the mac and cheese cools, it will absorb all of the liquid and lose the "soupiness". Adding milk back in and slowly reheating it will bring it right back to life!