I have that Camelbak brush, but I got sick of trying to use it to remove the crap from my Camelbacks. I rarely use them. I have used the brush forwater bottle tops, before they go into the dishwasher.
I use denture tabs for my Invisalign retainer. Even with brushing after soaking, there is always a gross film of stuff on them. It's not mold, so I have given up.

