What is the best way to reheat a sub-style sandwich?
So you go to a deli, pizza place, or any number of places that will sell you a 12"+ hot sandwich (e.g. a philly cheeseteak). You eat half and save the other half for another day. When that other day comes, what's the best way to reheat it?
For many other foods, the most common ways are microwave, toaster oven, regular oven and skillet. Unconventional ways I can think of would be steaming and sous vide (though the latter seems excessive for a sandwich).
The goal would be to get the sandwich hot enough to remelt any cheese, but to not render the bread too mushy or too crunchy (toast).
What method or combination of methods would you recommend to reheat a sandwich from the refrigerator? Be sure to specify whether you'd use higher or lower temps or power. If no one method would work well for all sandwiches, could you post guidelines?
The truth is, there really is no good way to reheat such sandwiches. The bread will have gotten soggy while the sandwich was in the refrigerator, and the densest part (which requires the most energy to get hot) is on the inside.
The option which is probably the least poor is to use the microwave, as more of the energy will be transmitted to the filling directly than with other heating methods. This is still likely to leave the bread kind of mushy and rubbery.
Your best option is to only buy the size of sandwich you want to eat, or to split one with someone.
Note that you mentioned store bought subs. If the sandwiches are homemade, there is a good answer: don't assemble them until you want to eat them.
You can then toast the bread, and heat the filling separately, and then combine them, and thus have a very fine sandwich.