I use Food Saver bags. They are rated for boiling water. I take my pulled pork and use a scale to divide it into 12 oz packages. There are two of us, so that makes two huge 6 oz sandwiches. I freeze these and then vacuum seal it (the pulled pork is too juicy to vacuum pack until it is at least partially frozen).
Weeks (or months) later, I put he frozen bags into the boiling water for about 20 minutes. When you initial do the smoke, you cook the pulled pork to near the boiling point of water (typical finish temps are in the 195-205 degree range), putting the pouches into boiling water won't change the character of the finished product. For other meals that would be ruined by heating this high (like tri-tip, which I usually cook to 145 degrees), I use something which controls the temperature of the water.
I have two different devices that I use. The first is a homemade version of the sous vide device someone already mentioned. This is a modified crock pot using a probe and temperature controller that I built (I need to use that EE degree I got forty years ago). I use this when I need precision control, down to 1 degree. For more approximate heating, I have a little induction cooktop that has pretty decent temperature control, and I can set it to 125, 150, or 175 degrees. I set it to one of those temperatures, fill a saucepan with warm water, and then immerse the vacuum bag in that.
Any one of these methods sure makes for some easy, but amazingly tasty leftover meals.