I have read of people using bleach on tank items. They never have a problem. But I would never do it. I know with my luck I would kill everything in the tank.
I have always used bleach for my white items. I had a few white plastic plants as well as 3 pieces of fake coral.
I simply place a glass juice glass upside down in my sink over the drain and then place my dirty items in the sink. I then put some bleach in the sink and then fill the sink with warm/hot water and let it soak for a few minutes. Once it's done I drain the sink and then plug the drain and fill it up again with fresh water and let everything soak for a few minutes again to remove the bleach.
I then drain the sink again and then take the hose for the sink and rinse off each piece again. I've been doing this for 12 years with no problems.
I used to use a toothbrush with my plants but it wouldn't work too well where there were seams. That's why I went the bleach method and haven't looked back. I don't use bleach for my colored plants, I leave them as is. BTW, I no longer use the white plants anyway.