You'll probably get better results if you search it online yourself as I don't know which type you're using, but I might as well show you what I found.
Best way to clean something like a coffee stain on a map is probably by using dish soap and scrubbing it. If it doesn't work use a designated stain remover product like OxiClean and such. Also, to answer your question they should be machine washable, but read the instructions just in case they can't. If you decide to machine wash it tho, be careful with it and don't just throw it into the washer. If you can't find the instructions you can also contact the manufacturer.
"If the stain is minor, such as a spilled beverage, you should use the dish soap method. However, if the stain is tougher to remove, like barbecue sauce or ketchup, you should use OxiClean. "
"Most trading card playmats can go in the washing machine. That being said, we always recommend reading the manufacturer’s instructions to ensure whether or not the particular mat you’re using can go in the washing machine. "
Source(read it for more info): https://indoorgamebunker.com/how-to-clean-playmats-pokemon-mtg-and-yugioh-trading-cards/
