Cleaning plastic furniture

http://homeguides.sfgate.com/clean-deep-stains-white-plastic-furniture-94707.html

Try Bar Keeper's Friend.

https://youtu.be/DeLOgoTwDAQ

Bleach maybe.

I have used the CLR outdoor furniture cleaner. It works well, we have to do it every year. If the stains are old and deep set -they may not come out. I do see here on Amazon this product has mixed reviews

https://www.amazon.com/dp/B002J9FVT0/ref=asc_df_B002J9FVT05308568/?tag=hyprod-20&creative=394997&creativeASIN=B002J9FVT0&linkCode=df0&hvadid=198091631239&hvpos=1o4&hvnetw=g&hvrand=4247593819484277856&hvpone=&hvptwo=&hvqmt=&hvdev=t&hvdvcmdl=&hvlocint=&hvlocphy=9008412&hvtargid=pla-349131319374#customerReviews

I clean my outdoor furniture with Heavy Duty Easy Off -- outside on the driveway (removing grime from the driveway also). Works every time and removes YEARS of grime and, of course, I meant for that to rhyme! (Sung to the tune of . . ..)

Thanks for your messag. But I ‘m in India where such stuff are not availabl.

I have 20 year old outdoor furniture that I cleaned this summer with TSP and a wire brush, sanded rough spots and spray painted in bright colors.