Answer:
<u>who bought me a soda</u>
Explanation:
Adjective clauses are groups of words consisting of at least a subject and a verb and whose function is to modify or describe nouns. They tend to begin with a relative pronoun (<em>who, whom, whose, that, which</em>) or a relative adverb (<em>when, where, why</em>) which can be the subject of the clause. “who bought me a soda,” then, is an adjective clause because it describes or gives us information about the noun “the guy” and it also has a subject (in this case, “who” and a verb (“bought”).