Floormat

Overtime, you car starts leaking... Or things spill. If you don't partuclarly want mold to grow, you can switch to rubber floormats

The issue is that if you have mud/water, it will sit on top of the rubber, but they are easier to clean in contrast.

I recommend to get a cutable rubber one like this: BDK Heavy Duty Rubber Cargo, Amazon, $30