Plastic patio furniture may get a bad rap in the decor world, but there's no cheaper way to seat lots of people outdoors. The main problem isn't a stylistic one, though. It's that plastic is porous and can hold onto dirt like there's no tomorrow. For a particularly stubborn stain, the vinegar treatment and standard soap-and-water didn't help. I even tried tile cleaner, but all I got was a headache.
I had a few Magic Eraser sponges (swear this is not a product placement) in my cleaning cabinet and on a whim, used it on the stain. To my surprise, it removed the stain with minimal effort. Just don't rub too hard, because I noticed that the sponge can dull the plastic surface.