It's possible you meant "complement" which is a word used to describe something that completes or enhances something else. However, there is no complement in this sentence.
It's likely that you meant "complement" as a grammatical term. In grammar, a complement is a word or phrase that completes the meaning of a verb or adjective. In this sentence, the complement is the object of the verb "make", which is "Sidney upset".
Here's a breakdown:
* Verb: make
* Object: Sidney upset
The object "Sidney upset" tells us *what* the teasing made.
Let me know if you have any other questions or if there was a different word you were thinking of!