【Heat Countermeasures】Freezing homemade sports drinks for baseball cheering! Can it keep cold?

Cheering for youth baseball under the blazing sun. For hydration, I froze a homemade sports drink and put it in a Thermos wide bottle, measuring the temperature for 6 hours. Can it keep cold?

Managing beverages when staying outside for nearly 6 hours in the heat of midsummer

Supporting my son's baseball team often means spending the entire day on a sun-drenched field. Until now, I simply let him take water or sports drinks in a plastic bottle, but as time passed, they would become lukewarm, and I noticed that the amount he drank decreased as the game went on.

When you're outside for nearly 6 hours in the intense summer heat, managing beverages can significantly change the risk of heatstroke. So, I decided to prepare everything by myself for the first time.

Preparing homemade sports drinks in a Thermos wide bottle

What I prepared was the Thermos "Vacuum Insulated Sports Bottle FJS-1000F." With an opening diameter of about 4.5 cm, its wide design allows for ice to be added directly, which was a decisive factor.

For the contents, I made a homemade sports drink by dissolving 2-3 tablespoons of sugar, about 1/2 teaspoon of salt, and 1-2 tablespoons of lemon juice in 1 liter of water.

The recipe and measurements were adjusted based on how to make oral rehydration solution, tasting along the way to ensure it wasn't too sweet but still satisfying. Measuring the salt and sugar with measuring spoons and mixing them until they dissolve well in the bottle is a bit of a hassle, but it turns out to be cheaper than buying commercially available bottled drinks. By adding the acidity of lemon, it avoids being a monotonous taste of just sweetness and saltiness, making it refreshing to drink even in the heat.

Being able to control the amounts of salt and sugar yourself is reassuring compared to just pouring in commercial sports drinks. In our house, I thought it might be nice to reduce the sweetness a little to suit my son's taste.

In the morning, fill the glass with ice before pouring in the drink.

Just before heading out, pack the bottle full of ice and pour in the freshly made drink. Thanks to the wide mouth, both the ice packing and the pouring of the drink went smoothly.

When I had my son taste it, he said, "It's sour but delicious." He seemed a bit surprised at the lemon's acidity, which is different from commercial sports drinks, but he drank it down readily, which was a relief.

Immediately after pouring, I inserted the thermometer and confirmed that the temperature had dropped to about -4°C thanks to the ice. If I spend a day in this state, will I be able to drink it cold until the end?!

What about the temperature change when I put the bottle in the specially designed case and placed it on the stadium fence?

I carried the bottle in its dedicated carrying case. By placing it on the game fence, it was always within easy reach. Under the scorching sun, my son, who got thirsty during the cheering break, and my younger sister who came along, were drinking eagerly from the wide mouth.

Just having the bottle in a place where the children could casually reach for it at their own timing seemed to change how I felt a bit.

Since it was a good opportunity, I decided to insert the thermometer and record the temperature at intervals. Immediately after making it, it was about -4°C, but what happened after that?

After 2 hours, it kept around -3℃.

Even after 4 hours, it was only slightly below -2℃, and

6 hours after the match ended, although the ice had mostly melted, the temperature was still below 0℃. The official spec for this bottle states "for cold preservation, guarantees below 9℃ for 6 hours," but in reality, it far exceeded that result. Since it could be confirmed as a number rather than just a feeling, I was relieved for the full 6 hours. I didn’t have to worry about it getting lukewarm.

Was 1L enough?

After the match ended, about an hour later, I checked the bottle 7 hours after departure and found that there was only about 2cm of liquid left at the bottom, almost all consumed. For one child to spend 6 hours in the blazing sun, 1L might be just the right amount—not too much, not too little.

If planning to share among multiple people, based on these results, preparing just under 1L per person seems to be a safe line, ensuring there is likely no concern.

The reason I chose this and what has changed after using it

The decisive factor for selecting this bottle was its wide mouth that allows ice to fit in and its simple structure that lets me choose the contents myself. While it does not have any special specs, I felt that the practicality of "this seems safe enough to rely on for a whole day" was the key decision point.

What I found good after actually using it was that I no longer had to repeatedly remind the kids to hydrate during cheering. As long as I have the bottle ready, the kids can drink at their own pace.

The biggest gain was that I could concentrate on cheering under the scorching sun. I plan to prepare the same way for the next match as well.

Product Name / Vacuum Insulated Sports Bottle FJS-1000F
Price / 4950 yen
Actual Capacity / 1.0L
Mouth Diameter / 4.5cm
Body Dimensions / 8.0×8.5×27.5cm
Body Weight / 0.5kg
⚫︎THERMOS

Interview and Text / SYURI

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