By two o’clock in the afternoon, the asphalt outside the stadium looked liquid.
Mika could feel heat radiating through the soles of her shoes as she crossed the service entrance. The summer festival had brought thousands of people into the city, and the temporary food stalls were working without a break. Even under the tent, the air barely moved.
Her supervisor, Sato, handed her a bottle of water.
“Drink.”
“I’ve been drinking all morning.”
“Then drink some more.”
Mika laughed. “I thought too much water was dangerous.”
Sato shook his head.
“That depends on the circumstances. Heat illness isn’t simply about not drinking enough water. You lose water and electrolytes through sweat, and what you need depends on how much you’re sweating, how hard you’re working, and how long you’re exposed to the heat.”
That summer, Japanese workplaces had been paying more attention to heat illness than ever. The Ministry of Health, Labour and Welfare had introduced updated workplace guidance emphasizing the heat index, early detection of symptoms, and procedures for preventing mild heat illness from becoming life-threatening. Official figures for 2025 showed 1,803 workplace heat-illness cases involving death or at least four days away from work—the highest number since the statistics began. (厚生労働省)
Mika looked toward the thermometer mounted beside the kitchen entrance.
“It’s only thirty-six degrees.”
Sato pointed at another display.
“Look at the WBGT.”
The number was considerably more alarming.
WBGT—the wet-bulb globe temperature—takes humidity, radiant heat and air movement into account as well as air temperature. On a humid summer day, the human body can struggle to lose heat through evaporation even when the thermometer reading doesn’t seem extraordinary.
Mika took another sip of water.
Then she noticed Sato opening a refrigerator.
He pulled out a can of cola.
“You’re drinking that?”
“Eventually.”
“Isn’t cola the worst possible thing?”
Sato smiled.
“That’s what people say.”
He had heard the same argument many times: water was supposedly insufficient because it contained no salt; sports drinks were supposedly ideal because they contained electrolytes; cola was supposedly a secret weapon because its sugar provided energy and its caffeine provided stimulation.
The truth was less dramatic.
Human physiology rarely fit neatly into beverage advertisements.
Water was perfectly useful for ordinary hydration. But during prolonged, heavy sweating, replacing electrolytes could matter. The body’s intestinal absorption of sodium and glucose is also the physiological principle behind oral rehydration solutions: sodium and glucose work together to promote absorption of water in the intestine. (世界保健機関)
That did not mean everyone working in summer heat needed to add salt to every bottle of water.
And it certainly did not mean that cola had somehow become an electrolyte drink.
Sato took a sip from his can.
“Cola has sugar,” he said. “So if you’ve been working hard and haven’t eaten, it can provide carbohydrate. It has caffeine, too. But that doesn’t make it a superior hydration drink.”
“What about the bubbles?”
“What about them?”
“I heard carbonation makes you sweat.”
Sato laughed.
“That’s the part I don’t believe.”
Carbonation could make a cold drink feel refreshing. A cold beverage could also provide a small amount of thermal relief. But the idea that the bubbles themselves reliably triggered sweating and therefore cooled the body was an oversimplification.
The important cooling mechanism during exercise in the heat was evaporation of sweat from the skin—not simply the sensation of bubbles moving through the mouth.
Sato pointed toward the open side of the tent.
“And that’s why the fan matters more than the cola.”
A large industrial fan was blowing across the workers.
Air movement increased evaporation, provided the surrounding air was not already saturated with moisture. Shade reduced radiant heat. Rest reduced metabolic heat production. Appropriate clothing helped. And drinking fluids prevented dehydration from becoming another burden on the body’s cooling system.
The drink was only one piece of the puzzle.
Mika finished her water.
“I still want your cola.”
“Fine.”
He handed her the can.
She took a swallow.
The sweetness hit first, followed by the familiar fizz.
For a moment, she felt better.
But it wasn’t because cola had defeated summer.
It was because she was sitting down.
The fan was blowing.
The sun was no longer directly overhead.
And she had finally stopped working.
That distinction mattered.
A beverage could help. Food could help. Electrolytes could help when they were actually being lost in substantial quantities. Carbohydrate could help someone performing prolonged physical activity.
But no drink could compensate for remaining outside in dangerous heat without adequate rest.
By the end of the afternoon, the organizers had changed their procedures. Workers were checking the WBGT regularly. Breaks were scheduled rather than left to individual judgment. Water and electrolyte-containing beverages were kept cold and accessible. Anyone showing dizziness, nausea, unusual fatigue, confusion, or other warning signs was removed from the heat immediately.
The cola remained in the refrigerator.
Nobody banned it.
Nobody called it medicine, either.
At sunset, Mika watched the last sunlight disappear behind the buildings.
“It’s funny,” she said.
“What?”
“All those arguments about which drink is best.”
Sato nodded.
“In extreme heat, people want one perfect answer.”
He looked at the rows of bottles in the refrigerator.
“But heat illness doesn’t work that way.”
The most effective strategy was not a miracle beverage.
It was recognizing heat exposure early, replacing appropriate fluids and electrolytes when necessary, eating when energy was being expended, reducing physical workload, increasing air movement, taking breaks, and getting out of the heat before symptoms became severe.
Mika picked up her water bottle.
Then, after a moment, she reached for the cola too.
Sato raised an eyebrow.
“Still want it?”
“Of course.”
He laughed.
“Fair enough.”
The cola was not a secret cure for dehydration.
It was simply cola.
And on a brutally hot summer afternoon, sometimes the most important thing was knowing the difference.
All names of people and organizations appearing in this story are pseudonyms
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