Vinegar

In MD, which is Humid in the summer, I use a vinegar solution for the plastic and seat parts that get moldy sitting in my garage.

Another is Hydrogen Peroxide. which turns into H20(water) as it works...You can buy it H2O2 - used commercially food applications...way higher concentration than the 3% sold for medicinal application, I think it's 20-30%, can't remember the exact number --- think hair bleach strength. Don't get this stuff on your skin...dilute it.

I use the 3%, which can be bought in gallons, for cleaning around the house rather than clorine bleach --- Basically H2O2 is the Active Ingredient in OxyClean, heavily marketed cleaner/laundry additive that costs 20X more than the cost of the active ingredient.

Either way--- Vinegar or and H2O2 varient---You will need to extract the water from the car...running a DeHumidifier with the windows shut.

Best and safest is vinegar --- I've used it to clean up a coffee with cream spill unto the back seat carpet...cream the worst smell possible as it get sour/rancid

more than you want to know, I'm sure.