I want to travel to Japan and Korea. I don't know if the habit there is to drink boiled water or wine.

In Japan, when you go out to eat, you are given water with ice cubes all year round. I was not used to it when I first went. I had a stomachache on the first day, but the stomachache medicine in the convenience store was quite effective. It got better the next day, and it never hurt. Or you can buy a thermos. Hotels or homestays have hot water kettles, so you can boil your own water.