Have you tried Boric Acid ?
Take half a cup of borax or boric acid, half a cup of vinegar, and 2 cups of water.
Add borax and vinegar to water and mix thoroughly.
Wash the shoes in this solution. For non-washable shoes, spray the mixture.
Wear the shoes only after they are completely dry.
Have you tried Baking Soda ?
Take two tablespoons of baking soda (sodium bicarbonate).
Mix the baking soda in 2 liters of clean water and soak your feet in the solution for 20 minutes. Pat your feet dry with a clean towel.
Sprinkle dry baking powder on your feet before wearing footwear.
Have you tried Vinegar and Alcohol ?
Take ½ cup of kitchen grade vinegar and ½ cup of isopropyl alcohol.
Mix vinegar and isopropyl alcohol together. Apply the mixture on your feet.
Let it sit for a while until it dries, do not wash the feet.
Have you tried Epsom Salt ?
Take two teaspoons of Epsom salt and about 5 liters of warm water in a bucket.
Mix the Epsom salt in the warm water and soak the feet in this mixture for 15 to 20 minutes. Repeat the remedy every night for a few days before going to bed.
Black Tea is said to help well too
Take 3 to 5 black tea bags and remove the strings and tags.
Take a half a bucket of warm water. Add the tea bags and leave it for 20 min.
Soak your feet in the tea decoction for 30 minutes. Repeat the process for a few days once before bedtime.
The tannic acid content in black tea that has astringent properties is just what you need to get rid of the foul smell emanating from your feet.
Regularly treating your feet with tea decoction helps keep them free of infection and helps remove the bad odor as well. Astringents work on the body tissues and help them control the sweat glands, thus reducing the profuse perspiration in the feet.

Go barefoot when he can, as often as he can. Wash regularly, maybe a good regular soak in smelly feet treatment. And try wiping with apple cider vinegar, the one with the mother in it

My feet smell like a dead animal after work, I actually started looking for something dead until I discovered it’s my shoes. I have no idea why!

Not wearing the same shoes every day may help and air his shoes!

Make sure shoes have a chance to dry out completely. Cotton socks changed regularly, and tea tree oil on the feet to kill any bacteria or fungus.

Great ideas ,will be putting them into practice

So glad to,read some of these solutions. Gave a smelly feet problem of my own :/ Fingers crossed we find something to help

I have sweaty feet and can often be smelly (depending on my shoes) so I plan on reading through these answers. Thanks for asking!

Will try the vinegar also ,one way or other I will cure his smell

Soak feet in Vinegar, and buy natural fiber socks

socks! wear them! biggest cause of smelly feet are no socks. make sure when he takes off his shoes that they get air into them and maybe even some sun. Wash them regularily

Helpful ideas ,one of these replies must work ,Cheers

I soak my partners feet in bicarb vinegar and a little bit of soap in warm water… Helps get rid of the dead skin

First wear cotton socks only, sprinkle bi card into shoes shake about and empty out, change shoes daily as shoes need 24 hrs to dry out properly. Every morning before putting socks on sprinkle a small amount of cornstarch powder on your feet

I agree with BUGGERITLIZ and also MEL 1 ‘s tea tree.
Good old bi-carb soda, great for taking smells out of the carpet and great for shoes tooo.