Clear liquids. This depends in part on what is the cause of the upset stomach. Breads tend to be a little harsh and may increase acidity. You will be safer with clear liquids, juices, jello, ginger ale and some find relief with pudding and ice cream. Most stomach upsets are short term but if you have a consistent problem you should see your GI doctor.
Ginger. I agree with dr. Bensinger. In additional to a clear liquid diet, consider a traditional chinese medicine tonic. Ginger is excellent for nausea and relieving smooth muscle spasm in the GI tract. You can drink slightly flattened ginger ale or freshly made ginger tea. It is quite helpful. Take care.