How do I disinfect a donated bedside commode?

Yup, bleach water is the way to go. It's what we used to disinfect the puppy and kitten cages at the humane society shelter I volunteered. Here's the CDC's recommendations on the right ratio of bleach to water: http://emergency.cdc.gov/disasters/bleach.asp

A cup of chlorine bleach in a gallon of water works just fine. Wear gloves.

Agree with Assandache. Bleach is one of the best (and cheapest) disinfectants around. If you live somewhere that the sun is actually shining set it out for a while after the wash. It's no more dangerous using a donated comode than using a public restroom so don't be afraid to accept one

I would use straight bleach and just scrub it down..Then finish with a mild soap wash down..