You can't wash this Buggle-up in the washing machine. Instead, a cloth and lukewarm water along with mild soap can remove a lot of stains. For stubborn stains, use a mild detergent for patio furniture without bleach. You can find these products at most home improvement stores.
Turn the cover inside out, zip it up and wash it in the washing machine at thirty degrees Celsius (about 80 ºF). Use detergent without bleach. And iron the cover after washing it. This will activate Sunbrella's properties again.