Indosole makes sandals out of old tires.

I tried buying a pair tennis shoes from them once, back when they were making a wider range of shoe types. However, my feet need more support than a basic "tennis shoe" offers, and their sizing runs a bit small, so it didn't work out so well.

At that time, they made their shoe soles by literally cutting the soles out of the sidewalls of the tires, but later they transitioned to grinding up the tires to mix with other types of rubber for recycling.

For a while, Indosole restricted their offerings to just flip-flops. Recently they have expanded to include these Adventurer Sandals that are a lot more like what I'd usually wear, and with very detailed sizing instructions, so they may be worth a look when my current sandals start to show their age.

The only main concern I have so far is that their FAQ claims the shoes don't do well when left in direct sunlight for a long time (due to using some natural rubber). This seems like an unfortunate weakness for a shoe meant to be worn during summer.