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The best thing to give, if you feel you have to give anything at all, would be a regular aspirin. Dogs can't have any medication that contains Acetaminophen or Ibuprofen in it as it causes kidney damage, so don't give either of those or medications that contain either of them.
Besides, Levaquin is a Quinolone antibiotic (levofloxacin) and is commonly used to treat bronchitis, pneumonia, chlamydia, gonorrhea and skin infections, so it would do nothing for reducing fever.
I hope this helps.