They specifically make very special pipe cleaner-like cleaning instruments for these things. Often, the bottle may even come with it. Very handy

Edit: this is the one I have

Although I only ever drink water out of it, I do make sure to wash up the straw at least once a week.

Thing is, that the straw plugs into a gasket on the bottom of the lid and is at least partly silicon all the way through to the spout. I make sure to run the cleaner brush thing through that very regularly as well. Sometimes several times a week just to make sure it’s always clean.

Yup, the pack of straws I bought came with a tiny bottlebrush thingy like the other comment linked.

Every water botulism I've bought that had a fancy straw came with a pipe cleaner and I'm leaving that autocorrect

A couple of things come to mind here:

I own a metal one which I assume was dishwasher safe but somehow water got trapped inside the 'extra' parts of it which could be unsanitary due to the water eventually stagnating.

Another is that the heat from the dishwasher can warp and silicone or plastic parts which will render them unusable eventually.

Not saying you're wrong but this is what I consider from the warning they provide.

I've seen a lot of fabrics that say "Dry Clean Only" because the manufacturer was too lazy, but my experience with dishes finds that the labels are generally quite accurate. Putting a non-dishwasher-safe item in usually ruins it.

Well yeah “Dishwasher safe” is an endorsement. The lack of an endorsement is not an endorsement to the contrary. Something is only “dishwasher unsafe” if it says “Hand wash only”

Eh, if the bottle is just for water there's enough spray and heat to kill and rinse it usually.

How would they know what sort o bacteria you cultivate in your abode?

Usually things marked not for dishwashers can’t hold up to the abrasive nature of the detergent or the heat of the water over a prolonged wash cycle.

Dishwashers are not magical devices, they basically just spray sandy soap-water for a long time.