A fit of sneezing, snorting, honking and wheezing are not necessarily a collapsed trachea.  Pulling on a leash (which a harness should always be used), drinking too fast or excitement can cause reversed sneezing.  This is usually caused by a elongated soft palate that is thought to become temporarily misaligned.  It is a common trait in toy breeds.  

Although this may appear to be scary, it only last a few short seconds or minutes and can be ended by massaging the dog's neck and throat and encouraging the dog to swallow.  Other ways to slow the reverse sneeze is to clap your hands, distract the dog or close off the dog's nostrils with your fingers, simply forcing them to breathe through their mouths and to swallow.