If you have a disposer in the sink, run that (with running water) while you are pouring the bleach, which throws the bleach combo everywhere. I tend to fill the sink with warm, soapy, bleach water. When it is almost overflowing and then pull the plug and turn on the disposer. It works well for me.
If you have a bathroom in the basement that rarely get used, be sure to run water in the shower and sink and flush the toilet once a week. This helps keeps things in working order as well as prevents a stinky dried-out trap in the pipes.