Iron Stomach
Having a stomach that can handle spoiled food or drink and not be affected by it
Joe ate some pizza this morning from several nights ago that was left out, and on top that he also ate some cereal with spoiled milk and did not get sick, he has an iron stomach
Iron-Stomach
When someone mixes vodka and cider and proceeds to drink it.
Tim over there has a iron-stomach after mixing vodka and cider and drinking it.