Acute gastric dilatation is a rare but critical condition with rapid and massive expansion of the stomach. In a 17-year-old man, it occurred after competitive overeating of hamburgers and carbonated drinks, which led to subcutaneous and mediastinal emphysema. After insertion of a nasogastric tube, the patient developed hemodynamic instability and oliguria. Urgent exploratory laparotomy aspirated 3.6 liters of stomach contents. The patient gradually recovered under supportive care. Cases of acute gastric dilatation after rapid consumption of carbonated drinks with subsequent pneumomediastinum are rarely reported in the literature. In patients with abdominal symptoms after overeating, timely decompression of the stomach is essential. The onset of hemodynamic instability or oliguria requires urgent surgical intervention.