Maybe you guys already know this but I didn't. When I had left over turkey or pork butt I was always disappointed a few days later when I wanted to make a sandwich.
After warming the food up the meat was always tough.
I had this idea and took some turkey gravy and brought it to a boil, removed it from the heat and then added the turkey and didn't reheat it.
It was just as tender as when we first cooked the bird.
I've also done this with BBQ pork only I used BBQ sauce and added water to thin it out. Works.