ABSTRACT Hyponatremia is acute when present for <48 h. Most cases of acute hyponatremia involve both excess free water intake and an at least partial urinary free water excretion defect. By contrast, hyperacute water intoxication may result from a large excess electrolyte-free water intake in such a short time that properly working urinary free water excretion mechanisms cannot cope. A hyperacute decrease in serum sodium may lead to death before medical intervention takes place. Well-documented cases have been published in the military medicine literature. In addition, news reports suggest the existence of cases of voluntary ingestion of excess free water by non-psychiatric individuals usually during ‘dare’ activities. Education of the public is required to prevent harm from these high-risk activities. Adequate training of emergency medical units may prevent lethal outcomes. Spanish media reported the case of a male who died following his triumph in a 20-min beer drinking contest. ‘From a heart attack. Man dies after drinking six litres of beer in a contest’ ran the news. We now review the physiology underlying hyperacute water intoxication and discuss the potential contribution of hyperacute water loading and acute hyponatremia to the demise of this patient.