alt Hacker News> The whole point of Thermos is to keep things warm for a long time. That means pressure.
That by far is not enough to forcefully yeet out the cap, probably not even if you take it to an Antarctic research base in -40 °C outdoor weather.
People forgetting about content that ferments however? Kaboom.
On a planet where fermentation exists, such as planet Earth, the only planet on which we, humans, reside and therefore where these containers are made and used, that means pressure.
Happy now?