After good quality stainless steel drinking bottles for kids. Need to be at least 400ml.
I saw the swell ones but they are quite expensive for something that is probably going to be lost - but if that is the only choice so be it?
Main thing with the stainless steel I'm aware you can get cheap ones from the supermarket and stuff like typo but the actual stainless steel used inside seems to be quite a low grade.
Something like this one
https://www.officeworks.com.au/shop/officeworks/p/studymate-…