[I]f the stomach’s emergency venting and emptying systems are out of commission – because the person is in a narcotic stupor, say, or dead—the organ will typically rupture at three to four liters, around a gallon. If you pour slowly, with less force, it may hold out for six or seven liters.
Very, very occasionally, the stomach of a live, fully conscious individual will give way. In 1929, Annals of Surgery published a review of cases of spontaneous rupture – stomachs that surrendered without forceful impact or underlying weakness. Here were 14 people who managed, despite the body’s emergency ditching system, to eat themselves to death. The riskiest item in these people’s stomachs was often the last to go in: bicarbonate of soda (aka, baking soda, and the key ingredient in Alka-Seltzer). Bicarbonate of soda brings relief two ways: by neutralizing stomach acid and by creating gas, which forces the TLESR [Transient Lower Esophageal Sphincter Relaxation, or burping]. (Less often, the stomach-inflating gas comes from actively fermenting food or drink. The Annals roundup includes a man killed by “much young beer full of yeast,” and two deaths by sauerkraut.)
Update from a reader:
You should google the genetic disorder called Prader-Willi Syndrome. People with this disorder do not get the normal signals to their brain that their stomach is full after eating. Eating until one’s stomach ruptures is one of the common dangers for PWS sufferers, and they occasionally die from it.