Updated: Nov 4, 2019
Your makeup sponges are just sponges therefore while they give you some of the greatest application benefits, they hold lots of product and absorb it.
To remove all of that you need to use an oil to remove the dirt. Like a facial oil or coconut oil, even a facial cleansing oil will work. Really let that sponge absorb the oil and squeeze it out to push as much foundation out as possible.
Do this repeatedly until you get out all of the product be careful not to poke a hole in your sponge!
That happens, when it does I suggest replacing your sponge.
However when you have gotten out all of that product, you can now clean the sponge with dishwashing liquid, laundry detergent or a brush cleaner.
I personally don’t use makeup brush cleaners because I find they are expensive but which ever product suits your budget.
After a good clean and your water is clear. Place on a paper towel somewhere clean and air dry.