it’s grammatically wrong to say: “In the refrigerator was a bunch of bananas and some milk”?
It’s incorrect. It should be:
In the refrigerator were a bunch of bananas and some milk.
The subject of the sentence is “a bunch of bananas and some milk,” which is plural. If the sentence is written correctly, it should be reversible:
A bunch of bananas and some milk were in the refrigerator.
See the explanation under the heading “Reversed subjects and verbs” at: