Tops are not left on bottles in any NFL stadium (or NBA or MLB arena) due to multiple throwing incidents including but certainly not limited to the Saints and the Turley incident. There are well-document others. This is stadium security 101. That's not to say a new employee won't let one slip out sometimes.
I'm all for innovative and/or humorous noise ideas, but the whistles are a bad idea and you might get a talking-to by security or ushers. Not to mention its just bad sportsmanship once they line up for the snap.