OP here. Thank you!
I've got them soaking in vinegar and water now, and will try washing with borax or oxyclean. I've tried all these in the past, but perhaps not in big enough quantities (ie, just a little scoop of oxyclean for load of wash.)
I do love to hang the laundry outside, but am not doing that this month because of our bad pollen allergies.

I guess I will have to start washing the stinky polyester stuff separately, just because of its tendency to contaminate the rest of the load.

Add some eucalyptus oil to the detergent used in washing machine. Am*zon has quarts for sale. I would start with about a tablespoon. Works for us.

Anonymous wrote:

Anonymous wrote:add a cup of white vinegar to each wash load. It helps remove the funky smell.

I've always wondered where you put the white vinegar in. In the bleach compartment? Or just directly into the basin on the clothes?

I put it in the fabric softener dispenser (I don’t use fabric softener though).

Workout clothes are washed separately with this detergent: https://www.target.com/p/hex-performance-anti-stink-fresh-clean-scent-detergent-50oz/-/A-50512969

It is the ONLY thing that was able to get the funk out of DH’s workout gear. I tried baking soda, oxiclean, and vinegar (I typically use these in the wash anyway), but Hex was the clear winner!

Anonymous wrote:add a cup of white vinegar to each wash load. It helps remove the funky smell.

I've always wondered where you put the white vinegar in. In the bleach compartment? Or just directly into the basin on the clothes?

Lysol makes a laundry sanitizer. Pretty powerful stuff if the other suggestions don’t work out.

add a cup of white vinegar to each wash load. It helps remove the funky smell.

Hot water and oxiclean. Just a dab of detergent and a bunch of oxiclean.

The reasons synthetic fabrics hold on to smells have to do with the way the fabric holds onto both bacteria and detergent residue. You could try a vinegar soak before you do the hot oxiclean washing. The vinegar is acidic (the oxiclean is alkaline) and it will remove the detergent buildup as well as get some of the bacteria, so the wash may work better.

20 Mule Team Borax works great and is cheap.

Nature’s miracle laundry boost does a lot for kid-related smells. I use the soak cycle with it.

The best thing I've done is use RLR on the sports laundry. It gets out all residues from detergent and other gunk. This is what holds onto bacteria and makes it nasty. RLR is amazing. https://www.amazon.com/RLR-Laundry-Treatment-Pack-3/dp/B007E24UOY/ref=sr_1_5?crid=OOXACFBXRC8X&keywords=rlr+laundry+treatment&qid=1557232642&s=home-garden&sprefix=RLR+laundry%2Cgarden%2C112&sr=1-5-catcorr

Rockin' Green makes a sports wash for regular laundry, to hopefully avoid it getting gross in the first place: https://www.amazon.com/Rockin-Green-Platinum-Powdered-Detergent/dp/B075MPKB9X

It may be too late for this pair, but in the future they need to go from the washer to dryer as soon as the cycle is finished. Don’t let them sit for any length of time.

Agree to try oxy and sun.

Put in sun to dry.

Soak in oxy clean overnight. Then wash and use fabric softener. Air dry. By themselves

my son loves these polyester Adidas shorts (mostly because he wants to look like everyone else). But they get stinky so fast!
They seem prone to getting an awful sharp sour smell. Washing them seems to accentuate it instead of getting rid of it. In fact, it spreads to the rest of the laundry! With other items, rewashing it gets rid of it. But with the shorts themselves, it seems like there is nothing I can do short of throwing them out. I've tried washing them on the sanitize cycle twice, used baking soda. I used to line dry them, but to dry them faster, I used the dryer. They still come out with that smell.

I've tried to drill it into my son's head never to wear them more than one day, and he's getting that.

Any suggestions?

And if not, are there any popular athletic type shorts that are less prone to developing a smell?