I've had success with Listerine. I reasoned that if it "kills germs that cause bad breath," it may well k.o. the ones that cause stinky feet as well. I applied Listerine all over my clean feet and wiped out the insides of my shoes as well (be sure to allow time for the shoes to dry out). At the end of the day when I've removed my shoes, feet and shoes have still been odor free.
Another Old Folks Remedy:
Isopropyl alcohol helps stinky feet. Apply with a cotton ball after each shower.
Twice a day, get a shallow basin, insert feet, and pour enough FULL STRENGTH WHITE VINEGAR over feet to completely wet them (though I use more, a half cup should do it) and let them soak for a few minutes. Tell your daughter to wiggle her toes and use one foot to wet the other.
Remove Feet (DO NOT RINSE) and throw away the used vinegar.
*I got athlete's foot when I was a kid. When we would drive home from Boy Scout camping trips I could NOT remove my boots in the car.
I tried everything available in the 1960s & 70s including:
Gentian Violet tablets (to make a soaking bath)
Mitchum Antipersperant (to prevent sweating and smelling).
When I became a doctor, I still had the worst athlete's foot--and foot odor--I had ever encountered. My feet sweated, itched and bled.
When my mother suggested the vinegar, I began soaking. At first the deeply fissured areas burned but the itching stopped almost immediately.
In addition to making an inhospitable environment for fungi, vinegar seems to act as an exfoliant. The mascerated (perspiration--logged) areas between my toes began to slough off and I helped it by using a washcloth wrapped around my finger to scratch, dry and debride the web-spaces.
As the deadened tissue was replaced, the slouging all but stopped, but I still intentionally rub off the loose skin on my feet when I dry them.
Today, I have pretty, odorless feet, and it even helped my toenails.
If your daughter decides to try this, you may want to rinse out her tennis shoes with vinegar to kill the fungi I suspect are growing there.
If she has leather shoes that should not be exposed to vinegar, try taking them to a local bowling alley. They may have UV lights that they use to kill germs on bowling shoes.
The main thing is to cycle her shoes regularly so that she is only wearing dry ones.
I hope this helps her.
Source: Peoples Pharmacy