home-made Drain-O. I've tried this before from other pins, but it seemed like all the foaming action bubbled up out of the drain... what a waste, I thought. The key to this is covering with a wet washcloth (why couldn't I think of that?).
Chlorine bleach is an effective alternative to commercial toilet-bowl cleaners. Add 1/4 cup to the toilet bowl, let stand a few minutes, brush with a toilet brush, then flush. This will disinfect as well. To remove a hard-water ring from the inside the toilet, pour white vinegar into the bowl and let set for an hour. Scrub clean and flush.