Tips for cleaning mousepad?

Hi!

I have a big desk mousepad that has sadly seen some better days (water stains, a tiny soda spill, etc) and I’d really like to know the best way to wash it. I’m sure it shouldn’t go in the washing machine (it’s kinda a collectors item, nothing too valuable but it’s not made anymore so I’d like to keep it intact!) but I just wasn’t sure of best methods for soaking etc. Thanks!!!