Drinking large amounts of sugary beverages like sports drinks can cause "PET bottle syndrome," leading to extreme thirst and fatigue.

This health risk is particularly acute during periods of intense heat, where individuals may mistakenly use high-sugar drinks as their primary source of hydration. When the body is exposed to high temperatures, the instinct to drink more can lead to a dangerous cycle of sugar intake that worsens dehydration rather than curing it.

Medical experts, including diabetes specialists, said that consuming excessive sugar causes blood glucose levels to spike rapidly. This shift creates an osmotic change in the body, which makes it easier for the body to lose water [1]. This process can result in symptoms such as persistent thirst, and general malaise [1]. In severe cases, the condition can progress to consciousness disorders or coma.

These warnings follow periods of severe heat across Japan. In some regions, maximum temperatures have exceeded 30 degrees Celsius [1]. Weather forecasts had previously indicated that severe heat would be widespread from western to eastern Japan starting from May 9, 2026 [2].

Public awareness of heat-related illness remains a concern. In a survey of 608 people [3], more than 50% of respondents said they had experienced the feeling that they might be suffering from heatstroke [4]. While sports drinks are often marketed for hydration, specialists said that the high sugar content in some varieties can be counterproductive if consumed in excess.

To avoid PET bottle syndrome, health officials suggest balancing sugary drinks with water. They said that monitoring the amount of sugar ingested during extreme heat is critical to preventing a medical emergency.

“Excessive sugar causes blood glucose levels to spike rapidly.”

PET bottle syndrome represents a paradoxical health crisis where the method used to combat heatstroke—drinking sugary sports drinks—actually triggers a different medical emergency. By increasing blood glucose, these drinks can accelerate fluid loss, potentially masking the symptoms of heatstroke while inducing a hyperglycemic state. This highlights a critical need for public health messaging to emphasize water as the primary hydration source over sweetened alternatives.