Answer: The function of the complement shown in parentheses (Sidney) is direct object.
Step-by-step explanation: A direct object is a noun, noun phrase or pronoun that acts as the recipient of the action denoted by the verb. Moreover, a direct object can only be present if the sentence contains a transitive verb. In the sentence "Did our teasing make (Sidney) upset?" "make" is a transitive verb, which means it demands an object. In that way, the noun "Sidney" receives the action denoted by "make" and answers the question "whom?".