It is possible to have dry mouth and an upset stomach due to gastroenteritis or food poisoning, which can result in vomiting and dry mouth. These side effects are sometimes caused by medications. These signs and symptoms can be noticed as part of the end-of-life care continuum. They can be noticed as a result of dehydration and poor intake caused by malignancies of the stomach, esophagus, ovary, pancreas, or biliary tract.