why wouldn't it? how would you clean it? how do you remove the taste of the cleaning agent? what if it's 2/3 days old. etc etc
how do you clean anything you drink out of?
how do you remove any cleaning agent normally?
water doesn't go off after 2-3 days inside a closed, dark container with no daylight. what would you do if you had a glass of water that was 2-3 days old also applies here but a glass normally has daylight impacting it which is the main thing which makes it start growing stuff.
however it looks like more than you are struggling with this concept so I'll leave this link here which google found for me
https://chillysbottles.zendesk.com/hc/en-us/articles/207411159-How-do-you-clean-Chilly-s-Bottles-
"We recommend cleaning your Chilly's Bottle regularly with hot soapy water and rinsing the bottle after each use. Please DO NOT use milton sterilising fluid as this can affect the products.
For a very thorough clean please use water with a teaspoon of bicarbonate soda. Whilst Chilly's Bottles are made of high-grade stainless steel which preserves the flavour of freshness of your drinks, if Chilly's Bottles and their lids are not cleaned it can lead to a smell or taste developing. For this reason, regular cleaning is highly recommended.
When not using your bottle, we recommend storing it without the cap on to allow the inside to dry out.
DO NOT put your Chilly's Bottle in the dishwasher or leave the bottle to soak in water for a long period of time. This can cause paint damage and can lead to the vacuum becoming ineffective."