Yes you can put milk into Chilly's Bottles. We recommend a really thorough clean straight after use with hot soapy water. For further cleaning please use bicarbonate soda.
When not using your Chilly's Bottle, we recommend storing without the cap on to allow the inside to dry out.
We do advise caution not to leave any organic produce such as milk or orange juice that can become spoilt in the bottle for too long as this may cause pressure to build up and potentially damage the bottle and cause lid failure.