"Let me be truthful with you" or "To tell you the truth" - what, have you been telling me lies before this???   Not exactly a business cliche, but I hear it too often in the office.

"Give me your elevator speech" - meaning, I want a very quick and condensed synopsis of what you are trying to do.

"Turn a negative into a positive" - okay, you fucked it up - now fix it.

"make some lemonade from these lemons" - see above

"this dog won't hunt" - this cliche is a good reason for not hiring management from below the Mason Dixon line.