I am pretty sure I got this idea from my beautiful friend Shannon off of her blog We, A Great Parade a few years ago. You should totally check her out, I get most of my ideas and inspiration from her.
So this is pretty simple. Take a teaspoon or so (you don’t have to measure, use more or less depending on what you like) of a mild soap, mixed with water plus a a drop of essential oil if you would like to add it. Give it to your child and they will have a blast spraying and washing. You will use less soap, you have control over the ingredients, it will save you money and your child will have a blast.