Does taking antibiotics help with a fever?

Yes: If it is a bacterial infection.

Possibly: If a fever is being caused by a bacterial infection, and that infection is being successfully treated with an appropriate antibiotic, then the fever should go down. If, however, it is a viral infection, a bacterial infection resistant to the current antibiotic, or a fever not caused by an infection, then the antibiotic will play no role in reducing the fever.