I would not use it, plastics can leach all types of chemicals, that's why most places don't reuse them. If you find a Cheese factory or something that used them for Calcium Chloride, I would be fine using them.

Car wash soap not so much, I have free access to Windshield Washer Solvent
55 gal barrels, called ChemTrec on that on and they said "That stuff is dangerous, i wouldn't risk it".

Hope this helps.