Refilling the bottles with store bought foaming soap is a bit more eco-friendly and cost effective than re-buying a new foaming soap container every time, but there is a better way: Make your Foaming Hand Soap at Home!
I purchased these 3 containers about a year ago and when they went empty, I refilled them with Castile Soap and water. It is that easy! Why pay for a container at the store that is mostly water?
I bought mine on Amazon : Castile Liquid Soap-Almond Hemp (Organic) - 32 oz. - Liquid
I chose the almond scent as it has a "grandma smell" to it. Grandma smells include almond scented Jergens lotion and Caress bar soap.
I don't have an exact science to it. I fill most of the container up with water and then add ~1 Tablespoon of the Castile Soap.
Foams like a charm! Try it out yourself! I don't think that you could fail poorly enough to where it doesn't foam, but depending on how "smooth" you want it, you may need to add more of the Castile soap.