The baby, 10 months old, started with dry heaves at midnight on the 9th, and by afternoon, the fever rose above 38.5°C. Despite taking fever-reducing medication, the fever recurred. By the third midnight, the fever reached 39.9°C, prompting a rush to the hospital. There, the baby began to feel nausea and vomiting, but did not dry heave. After two days in the hospital, the fever subsided, and now there is no more nausea or vomiting. The throat is inflamed and swollen, the baby cries frequently, refuses to eat, and lacks energy. The doctor diagnosed it as acute gastroenteritis and advised against drinking milk. How should it be treated?