I've got seatbelts that were stuck under the seat for a long time and they are kinda funky. THey are original and I just want to clean them. What's the best way?

Use your favorite cleaning product and some hot water. I have very good luck using simple green and then drying them off well.

Put them in an old pillow case and then throw them in the washing machine.

another option,
lay them in the top tray of the dishwasher ( when the wife isnt home )

Thanks for the suggestions. I ended up using a blue paper shop towel soaked with water and liquid hand soap. Worked great! Didn't even remove the seat belts. Just laid down an old towel.

I am a big fan of tide and hot water.

I have a small carpet shampoo unit that has an upholstery attachment. I use that with hot water and Resolve.

Takes the stink, mold and dust out - they look brand new when I am done. No need to remove them from the car.

True. I have a Bissell Big Green clean machine strictly for upholstery cleaning. Problem is it works so well I get obsessed and end up cleaning everything fabric in the car.

Chances the belts are dry rotted after so many years?

why ? NHRA allows factory belts to be used in certain classes, no matter the age.
but use race belts, they must be replaced every two years.
the factory belts must be of better quality materials.
[insert sarcasm here]

I rarely clean my seatbelts as it does not get that dirty easily compared to the seat but if I do I just use cotton dip it with water and tide and scrub it a little. I also use a toothpick and put small cotton on it to clean the latch.