hypothetically, I suppose one could pay attention to their bodies, because there are probably some anxiety signals taking place before the hypothetical vomiting begins. If one were very in tune with their bodies and any initial signals of anxiety (butterflies, increased heart rate, shallower breathing, etc), then one could try stopping what they are doing, and do some meditative breathing, focusing on nothing except breathing for 5 minutes or so.

If that doesn't work, then get on with your day and maybe call one's pdoc to discuss one's level of stress and anxiety.