Why do my kids water bottles for school stink?!

Why do my kids water bottles for school stink?

after a while the bottles smell awful although they are washed out. the drink inside gets contaminated and tastes like pond water. why ?

2 days ago
they dont pee in them lol, these bottles are made for re-using, they are sports bottles used in gyms but what is the point if you have to replace them every few weeks ?

I received an e-mail from a friend in British Colombia a couple of weeks ago, in which she quoted some research findings into plastic bottles with water in them.
It was warning against using them in any situation where the plastic might become heated (hot rooms, cars, etc) because of chemicals in the plastic leaching out into the water and possible detrimental long-term effects on the person who drank water from these containers.
The article went on to recommend that for any storage of drinking water, it would be better to use metal containers.
Is it possible that this is what is happening to your kid's water bottles?
If you feel this is probably another scare story and are happy to continue using plastic bottles, why not stand them overnight with a mixture of baby-bottle sterilising fluid? That would destroy anything causing the stagnant taste.