I would agree 100% with you if water was the only thing that ever saw the inside of a bottle/camelback ... however, as soon as any sugary drink is place inside the whole microbiomic repertoire is irreversibly altered. Personally, i don't think it 's a big deal in the long term, potential ingestion of bleach is much bigger deal, but a blanket statement that bleach kills everything is naïve, is it not?

FYI, certain microbes (particular nosocomial strains) are much more "bleach-tolerant" than they were even 5 years ago.