I have had good luck with "powdered dish washing detergent".
It has a disinfectant, bleach and a sheeting action/dryer in it.
Mix it with water and wash with a soft brush and rinse it off.
Not perfect but pretty good.
$1 a box at the dollar store.
Plus it does not hurt plants.
I use it for washing my camper, cleaning the pool/hot tub filter and many other things.
Gebhardt & Company Painting