Potato water soap! I made a 0% superfat coconut oil soap and used potato water for the liquid mixed with lye. How? Boil potatoes to make mashed potatoes or potato salad. Pour off the water and save it to make soap. I weigh my water and plug the amount into a
lye calculator with 100 coconut oil, 0% superfat. Make liquid soap as usual, I use a crock pot for the cook. The resulting liquid dish soap makes a ton of suds and cut grease easily on oily soap making dishes. I made a gallon which will last me a long time. I do have to wear gloves as the soap dries my hands but I like the cleaning properties better than Dawn detergent. See the picture of all the suds that foamed up while washing up from soap making.
I am assuming someone wanting to try this is familiar with liquid soapmaking so will understand how to develop a recipe. If you are looking for a natural dishsoap that really works, this is it.