I went ahead and disassembled one of my Camelback bottles. I've used this one for almost 3 years with sugary drink mixes. Zero signs of mold or gunk. Just a very slight bit of mineral deposits. on one of the o-rings.

As I mentioned earlier in this thread, I pull the stopper out and put that and the rest of it in the dishwasher. So either this is working well at cleaning out stuff or the fact I live in a dry desert area causes the parts to thoroughly dry out so mold never grows.

I much more suspect the dishwasher is simply cleaning it well.

Based on what I saw, I won't be bothering to disassemble mine again. There simply doesn't seem to be a reason for me to do that.