Heat your grilled steak in a Ziploc bag. The best way to reheat grilled steak is to use a Ziploc bag and submerge it in boiling water. In order to do this, you need to get a large pot half-filled with water, which you need to bring to a boil.o not forget to drizzle the top part of the steak with butter. Stop heating once the temperature is warm, but do not let it get very hot or overcooked. Reheat using beef broth. You can put your leftover grilled steak in a frying pan, then pour beef broth over it. Let the broth and meat simmer by turning the heat up.