Girls' 3.07 is either poisoning or a viral infection started. On July …

Girls' 3.07 is either poisoning or a viral infection started. On July 1st they were at the sea swimming and possibly drank water, says that the sea doesn't taste good. Vomiting since morning with foam or mucus, not clear, with clots. Temperature is absent. Before that evening she ate bought milk shakes, canned potatoes on chicken hearts, banana and cookies. In the evening diarrhea was a couple of times. She was drinking water, Regidron. By evening vomiting ended. The baby is cheerful. All day they didn't eat anything, only a few small fish crackers. What can you feed her??? (loves potatoes and macaroni). Doesn't like vegetables, cereals too not much