Its called rinsing with hot water a few times, to wash, then with cold water.

How else do you clean a water bottle?

It holds water... like whats in toilets.

Its not Brawndo

There is rubber/silicone/latex bristled bottle cleaners. I find they clean way better than those in the op comment, and they definitely don't scratch anything.

Do you not just wash it with a bottle brush?

the more stout variety of water bottle cleaning brush won’t bend and is super effective. these can be frustrating if the stuff you’re trying to dislodge is really on there.

I clean all my bottles with a bit of rice which scours and scrapes. Shake it vigorously with a bit of bleach and dish soap. Comes out spanking clean.

Came to say this - also good on stained mugs!

They also make them for glass and metal straws! I have several sizes of these brushes, also to clean tubular tea strainers etc.

Looks like hard water spots. Bar keepers friend will take care of them.

Are you running it through the dishwasher? I recommend hand washing it daily. Only takes 5 minutes.

In my household, we give Dawn Powerwash a try on just about everything haha.

It’s a hit.

Very recently I read the tip to use denture cleaning tablets for stuff like this. Haven’t tried it myself yet, but apparently it works wonders.

Tbh I would just throw it away and next time u get a bottle make sure it can fully be scrubbed. 

Use uncooked rice with some dish soap and water. Shake it all around in there.

Denture tablets can be good

Salt can work as an abrasive! Just use cold water and way more salt than can dissolve and a little drop of dish soap. Shake it up for a while and most stuff should come off.

That’s most likely mold. I had some of the same looking stuff on my water bottle that would not come off, even after being soaked in soapy water for hours. I just ending up getting a new one

It’s mold. You can’t My recommendation is to a to go for the simplest kids possible. Avoid anything that has a straw/sucky thing at the top. Also look for pure stainless steal with no plastic coating like this. It’s easier to maintain and will not have this issue.

Buy a straw cleaner, looks like a little pipe cleaner. Soak the cap in boiling hot water to loosen the grime. Use the straw cleaner to get into the hole with a bit of soap and scrub it clean. Check the rest of the bottle including all seals. Then follow these steps to sanitize and disinfect

https://www.clorox.com/learn/how-to-clean-sanitize-water-bottles-with-bleach/

just classic water bottle muck and gunk, you can get a q-tip and wipe it off

Honestly, I'd throw that away and buy a new one. Then I'd make sure to clean the new one thoroughly and often. You could clean it using the advice you've been given here, and it would be fine... I'd just never feel right about drinking from something that had gone moldy.

Denture cleaning tablets. Soak it over night. They are great for cleaning, especially things in hard to clean places…..water/coffee bottles, tank of coffee maker, uses are endless and they are also antibacterial

My bottle top gets like this, I use a bottle brush, its like a long thin wire with brush bristles on the end. Works well on the straw too if there is a straw attached. I think it was a couple of quid.
I also found I could pop the mouthpeice off carefully which made life easier, but this is at risk of breakage.

Vinegar will dissolve it if it is mineral deposits.

Yeah for vinegar spritz. A quick spritz of stuff and it’s all shining. Rinses easily, won’t do you any harm anyway. Yeah for vinegar spritz.

I get this too. I put white vinegar in a plastic jug and immerse the top for about 15 minutes. If there’s any still there after that, it will just wipe off.

Yeah bottle brushes are the way to go. I've never tried vinegar, I normally just use soap and then a lot of rinsing

Bottle brushes and white vinegar. I bought bottle brushes with wire handles so they fit through the hole easily and can be bent to clean hard to reach areas.

You can use a descaler to clean it but if you live somewhere with hard tap water, it'll be difficult to avoid. It's nothing to worry about, though, just slightly unsightly at times

I have hard water in my faucets so I just wipe down my cups

water stains, probably mineral deposits. if you don't like them just use distilled water for cleaning and drinking.

Hard water. No biggie! They probably wipe off.

They’re minerals, Marie.

Use dish soap and a bottle brush. Sometimes I use denture cleaning tablets and hot water to deep clean them.

They sell straw brush and bottle brush in pairs nowdays. Use the skinny straw brush, wet with dish soap, to wash the inside of the straw and mouth piece. Use the bottle brush, wet with dish soap, to scrub the interior of the bottle. Make sure to let the bottle dry thoroughly before closing the bottle and storing. If you plan on using it immediately after washing, then you can skip that test. I would use a sponge to wash the interior of the bottle cap.

If you have a bottle with those rubber/silicone gasket rings in the lids, they make tools to remove them so you can wash those too. Mold can grow under those if you don’t remove them to clean them unless they’re glued on. I think manufacturers used to glue them on years ago, but with the rise in popularity with these insulated bottles, they’ve stopped gluing them on for ease of cleaning.

Don’t forget to memorize how they were on originally! If you but them back on wrong, you risk bottle leakage. I found out the hard way with a metal insulated soup thermos with a lid with a gasket. Chili juice and oil leaked everywhere in my lunch bag!

I put my hydroflask in the dishwasher and it’s been fine.

Hot water and dish soap. Detach the straw if you can. Run water through the straw and the lid. Use soap with a sponge on the outer straw part in the lid.

Basically, wash it like other dishes. Very basic stuff.

In with the other dishes, use a bottle brush with the test scrubbing attachment, basically a tiny little scrub brush to clean inside the lid. Rinse well.