Reheating brisket can be tricky, as it can easily dry out. - In the Oven: Preheat the oven to 275° F (you can also use a grill or a smoker like an oven). Double wrap the brisket in foil (add in a splash of beef broth or beef tallow to make it extra juicy) and place it on a sheet pan and heat until the internal temperature reaches around 165° F, 30 to 60 minutes. - Sous Vide: Vacuum seal the leftover brisket and place it in a 155° F water bath for 1 to 2 hours. Remove from the bag and enjoy. - Skillet: While it's going to change the texture a of the brisket a bit, heating it in a cast iron skillet is perfect when making brisket sandwiches or brisket tacos.