If its more then 10 years old, time for a new one. Then use a mattress protector so sweat etc can not soak into the mattress itself.
I got myself a new mattress and adjustible bed. Best investment ever.
PS "angry orange" may help with the smell of the old one on a temp basis.

If you are wanting to maybe get a little more life out of it, you could go over a few times with a carpet shampooer. That might help. Maybe.

Then just yeah once it dries, just throw on a matress pad and wash it regularly.

I think new mattresses cost a small fortune, I understand not wanting to replace.

My gyod I think they are like $1,000 brand new, I remember in the year 2000, we bought a complete brand new bed. It included box spring, mattress, and steel frame bed support all for like $600.

I don't think there is a way to clean a mattress. Sweat is one thing but body dander which creates mites is another. Any liquid will be near impossible to remove. Much cheaper to go to Costco and buy a new mattress and a waterproof mattress cover. The cover will protect the mattress and is washable.

Best idea if your going to the trouble of cleaning it, you can steam clean it but it will need to dry it in the sun to prevent mould, then you need a good mattress protector. Or buy a new mattress and good mattress protector. This way all you have to wash the sheets and mattress protector and this will save the mattress. Also get him to wash before bed.

Well, the community has dropped numerous good methods.

Here's an extreme measure.

Utilize this with PPE and maximum ventilation.
Isopropyl alcohol, and bleach. Parecetic acid. It will clean and deep clean, but it is a potent chemical compound.

Me? New mattress. Mattress cover. That's what I'd do.

Thank you all for your input :)

Reading all of your responses made me realize the idea of attempting to clean the mattress is akin trying to un-squeeze toothpaste lol

So, I decided to throw out the mattress. Get a new mattress for my son and have him use a mattress pad.

Just wanted to thank everyone for their thoughtful responses. :)

You can get a nice-enough cheap mattress online that would allow you to toss out the old funky thing. We got a new mattress a few months ago and it only cost a few hundred dollars, replacing both of our $2,000+ mattresses.

I would throw it out. You'll never get out all the bacteria. Start with something sanitary. And, you may consider getting a protective mattress pad for it. That can be washed. The mattress can't, really.

You can buy a cover for the mattress. It will keep cooties from living in it, and will also keep his sweat off. You may need to wash his sheets more often but that should work. Personally I would toss the mattress and get a new one, and add this cover.

A mattress pad my help a lot. They're machine washable and inexpensive to replace.

get a new mattress use mattress cover as others have suggested and investigate why your son is so sweaty in bed.... might need a conversation with him

I would buy a new one and use mattress protector also open all windows in the room regularly and use dehumidifier.
Perm room spray.
I assume your son takes shower everyday shave his underarms and use deodorant

Replace the current one and get a washable mattress protector for the new one - if a thin removable foam topper is possible that might help too.

It may be more practical just to buy a new one.
Take into account price and time involved in cleaning it , finding alternative sleeping arrangements for your son.
As it is , after years of use it's healthier to switch it.

Best to use a mattress protector, mistakes happen especially with children and the elderly.

Sprinkle baking soda with a few drops of essential oil. Let it sit to absorb the smell. Then vacuum up and finish by steam cleaning.

If the mattress is 10 years old or older then just replace it. For stains my wife uses a mixture of baking soda, Dawn dish detergent (the blue one) and hydrogen peroxide. It works really well on furniture stains. After drying I would seriously consider a removable mattress pad cover that you can wash in the washer. Of course if it's that bad I would seriously consider a new mattress. Definitely get the washable mattress pad too.

Could he sleep in a sleeping bag on the floor while the mattress dries or maybe put it outside when it’s really hot in the daytime and that would help speed the drying process.

Good luck

Likely toss it & use a mattress pad on the new one

Yes toss it and take the advice of mattress protector on next one

Baking soda can help! (=

Set it on fire, buy a new set and use a washable mattress pad or waterproof mattress protector.

I'm dead-serious

Just buy a new one

Steam-cleaning? Maybe one of those pet stain/odor removers meant for rugs and furniture? LOT of Febreeze?

Time to replace and ensure he respects the new one.

100% throw it out and get a new one.

Doesn't it have sheets and a mattress pad?

Time to visit Sleep Country!!

Throw it out and buy a new one. Simple.