we dont , we just trust the people that say its clean , there is no way of acctually finding out if you are drinking clean water in water bottles unless you specificly clean it yourself ! anyone dis...
To clean a water bottle you have to put fine sand into the bottle and then pour water and put one of your fingers to plug the bottle and shake for a little while and pour the sand and water out then...
To get it thoroughly clean, you need to empty what was in it first. DUH! Then you need to take warm water and fill the bottle. Let it soak for a few minutes to an hour depending on how clean you want...