Those bottles of water are not sterile, but they are usually free of
the common minerals like iron that frequently spoil an otherwise good
batch. If you are going to use bottled water you have to boil it to
kill everything. If you are going to use the container that it came in
for wort than you have to sterlize it. I prefer Iodophor and if you're
concerned about the taste of iodine then empty the sanitizer and rinse
it with boiled water (cooled of course).