Is my water bottle okay to use?

If it was me, I’d toss it. Too disgusting to think about drinking out of it even if I was able to fully clean it.

I wouldn’t use it until you get all the dark and slimy off. Try soaking in vinegar and a good scrubbing first. If that fails you can try bleach. Keep in mind though that plastic bottles may leach toxic chemicals into the water in them when they are used repeatedly. Using harsh chemicals like bleach or exposure to heat can accelerate this leaching. Some people think concern over that is overblown, and maybe it is, but if your bottle was exposed to extreme heat in the car window, or if you need bleach to get the gunk out, you might consider replacing it.

I have a Klean Kanteen bottle and it is great. Check them out.

Thanks, @erichw1504, I’m looking into others now. I’d like to keep using Wall-E for sentimental value and because it’s totally adorable, but health is also important. What I love about this one is that it’s light and easy to drink from, which seems to be a problem with many water bottles on the market now. I might get a CamelBak one with the straw and bite valve, but I’m still not sold.

Try soaking it in hot water with dishwasher soap.

And if you do toss that bottle, try this out.