reheating turkey breast slices

I would slice and reheat in a stovetop pan in gravy or at least broth. It should not take long. The meat doesn't need to be hot , just warmed through. The gravy should be hot when you serve

You could also reheat on low in gravy until hot. I don't know how important making sure the temperature is 165 degrees again, as the breast meat has already been cooked (and if you had sliced down for sandwiches, you wouldn't bring it back to 165 anyway). You especially don't want the meat to get dry and tough, which it could if you recook it for too long.