Actually, I recall accidentally catching a segment of the Bill Cosby show recommending to put an empty soda bottle in the toilet tank to save water. This was so idiotic that it stuck in my memory.

If you want literal shit to build up in your pipes, instead of fully flushed - go ahead and do that. Water saving toilet tanks do not function as advertised.

Taking a hot shower is also a treat, mental therapy, and one of the absolute greatest blessings of our technological civilization. Don't shortchange yourself.