Great question! So glad you asked.
Here's a quick tip: if you have used your reusable double walled stainless steel bottle to its absolute limit, it CAN be recycled. But do not just dump it in any recycling bin. It has to be taken to a scrap metal yard!
Finding a scrap metal yard can be done with a quick google (I'm not going to do that work for you it's a quick tip get it?).