i've scavenged some buckets from construction dumpsters. they had stuco, paints, and other such liquids used for normalizing and updating buildings. i wondered if i could store food in them. and i can, turns out.
according to this FAQ, buckets with a recycle sign with a "2" in the middle of it are good for storing food. the plastic needs to be inert to the point where foodstuffs and the plastic will not chemically interact. High Density PolyEthelene is a common plastic type that will work, and will sometimes have the abbreviation "HDPE" on it.