Eat several antacid tablets high in calcium. Last but not least slowly drink a large glass of water. Also try peppermint tea, or a peeled and grated potato strained through cheesecloth, added to water. Certain fruits have enzymes that calm down the most upset stomach. Try mango, kiwi fruit, papaya or fresh pineapple.
Gas can be a problem.
To relieve, try ginger or anise tea. If you like beans but they cause you problems try cooking them with a few slices of potato which seems to remove to gas, and has no affect on the taste of the beans. To control nausea, pick up and sniff a newspaper. An ingredient in the ink will quickly clear up that sick to stomach feeling for many people. Also try sucking ice cube or ice chips.