I've been a firm proponent of Klean Kanteen bottles for nigh on a decade now. The two I have have suffered a bit of abuse, scuffs and dings, which only marginally reduce the capacity. I think I could drop one off a building and it would survive.
The stainless bottle and the plastic cap are easy to clean. Sadly, over the years, the rubber o-rings that seal the bottles up and stops errant drips have degraded somewhat. I am not sure what the black stuff is, I can't clean it off and it looks pretty unsightly. Also, there are some tears in the rings which compromise them.
Thankfully, a replacement aftermarket set is available on Amazon and it is a quick job to whip off the old ones and replace them.
Ready for another 10 years of service.