Ensure brisket is completely defrosted before you reheat it.
Preheat oven or smoker to 250°F.
Wrap brisket in two layers of aluminum foil and place in heated oven or smoker .
Your brisket is done when it reaches 165°F which will take between 20-55 minutes depending on the size of your brisket and if you are heating a large chunk or individual slices.