There are 2 types of feet: those made of foam and those with padding only.
I don’t recommend machine-washing the feet, as the foam may deform. The padding will absorb a lot of water and could shift. I therefore recommend washing the feet by hand, in a bathtub.
Soak feet in cold water with a little soap. Gently rub the underside, which is usually the dirtiest part as it’s in contact with the floor. Don’t hesitate to soak several times in a row to circulate the water in the fur. You can scrub with a soft bristle brush. It’s difficult to remove all the dirt, and the fur may remain dirty-looking.
You can also wash the inside of your feet, since you’ve sweated there. If your feet are made of foam, soak them in water, then shake them off.
Once feet are clean, rinse. If you’ve cleaned the inside, don’t forget to rinse this area.
Drying: hang the feet upside down for an hour to flush out the water in the hollow part, then dry them right-side up. The inside may be difficult to dry, so don’t hesitate to use a fan.