However, it has been suggested to me that there are other possibilities. One was that it was a way of storing emergency drinking water or water for strangers to drink when they walk by. While these would be reasonable theories, they are not in keeping with Japanese thinking. No Japanese person would touch a drop of water that had been stored outside of their home, particularly in an unsealed bottle that anyone could come by and contaminate. Most of the people I spoke to were too suspicious to eat a free sample given away on the street, even a sealed one. There was a great deal of squeamishness about safety.
Also, it was not likely that they'd put water out there because it allowed them to store their earthquake supplies. Even if they wanted to use if as washing, cleaning, or toilet flushing water, they wouldn't store it in public. It is simply not done that way in Japan. It's not even done that way in most areas of the U.S., particularly not in suburbs. The desire to put on a "nice" front could only, apparently, be overridden by the scourge that is stray cats. I finally did do some research, and these bottles were put there because of cats. A Japanese T.V. show tested the theory because the habit is so common.
I don't miss seeing these bottles all over the place as I'm not a fan of people lining up trash in front of their homes in any country.