I never had these hot bottled/canned beverages, despite spending considerable time in Tokyo's subways. I was always concerned about what chemicals could leach into the beverage from the interior of the container, with the prolonged exposure to hot liquid.
Heat in general is not good for foodstuff, as it generally breaks down nutrients and creates free radicals.
Interesting, yes I can see why that might be a health issue. But these things have been around for decades now, so presumably they’ve solved this problem.
Edit: I found this:
IH vending machines
This is a type of vending machine equipped with Induction Heating. They store canned beverages at normal room temperature (or lower temperature) on standby and rapidly heat up a selected drink during the process of dispensing. It is possible to raise the heat up to 140 degrees or so in less than one minute in the case of a 250 ml can.
Heat in general is not good for foodstuff, as it generally breaks down nutrients and creates free radicals.