Have you ever had someone talk closely with you that had sinus breath?  It can set you back a bit.  Everyone has this issue at some point due to seasonal allergies, winter colds and more.

Make sure you take mints with you prior to any interview and pop one or two in before you meet with people.  Strong mints can have the same impact as sinus breath so choose hard candy peppermint or spearmint, or Tic Tacs or other moderate mints.  Also chewing minty gum beforehand can cleanse your mouth and provide fresh breath.  Just make sure and throw your gum away before going into your interview.