I think the correct answer is the third one, "I made the best brownies today!"
An unreliable narrator is a narrator whose credibility has been compromised. Since you can't tell if this narrator credibility has been compromised from a single sentence but need a whole text to develop such incredibility, I say this is unreliable because the narrator is giving its own opinion of something he/she has made, and you can't rely on he/she being imparcial.
