The values you wish to display in the dropdown can be put in a formula that you write anywhere in your workbook and then use to accomplish this with Office 365.
The formula would be:
=  TRANSPOSE(
       TEXTSPLIT(
               SUBSTITUTE( SUBSTITUTE( SUBSTITUTE( J2, """", "" ), "[", "" ), "]", "" ),
               "," ) )
Where J2 holds the retrieved JSON string, "Oranges," "Apples," and "Mangoes." (For example, "localhost:8080/api/v1/list" results)
For instance, if you enter that in cell D2, you can navigate to Data > Data Validation and select List with the formula =$D$2#.


A more readable version of the formula might be:
=LET( s, J2,
        s_cln, SUBSTITUTE( SUBSTITUTE( SUBSTITUTE( s, """", "" ), "[", "" ), "]", "" ),
        TRANSPOSE( TEXTSPLIT( s_cln, "," ) ) )