Add water to the foaming soap dispenser until it's about 2/3 full. Don't get it too close to the top, or it will overflow.

Add castile soap to the water. There isn't a precise measurement for this, I just add enough so the water rises up a bit. But again, don't get it too close to the top.

Add a few drops of peppermint essential oil.

Shake it up a bit to mix all ingredients together. Now it's ready to use!