Question:  Where is the condensate drain on the 1994 Jeep Grand Cherokee?

This is one that quite a few people have problems with.  Someone at Jeep thought it convenient to run the condensate drain into the longitudinal beam of the vehicle frame.  Thus, you won't find a drain tube poking out anywhere under the vehicle.  You'll find this design on 1993 though 1996 Grand Cherokee. 

The main problem stems from the fact that the air intake grill outside the vehicle is not fine enough to capture as much debris as it should.  Twigs, pine needles, etc, pass through the intake screen and clog the drain.  And yes, there's an updated intake screen to lessen the possibility or another blockage.  This clogged drain condition can lead to odor, sloshing sound in evaporator box and wet floorboard.

Here's the Gary Harrison method to get that condensate drain flowing again.

1. Pull the carpet on front passenger side back to expose the circular duct at the base of the firewall. 
2. Drill a 1/4" hole in the center of the circular duct outlet. Water may
   run out when you drill this opening.
3. Run a coat hanger wire or similar through the drilled hole, and down the tube to "rod" it out. Outlet is forward and slightly downward. 
4. After clearing the drain, fashion a plug from some handy material. Parts stores have various size rubber plugs. Hot melt glue might work.

Chrysler has a Technical Service Bulletin for an updated cowl screen.
See TSB: 24-17-97

Photo above shows the approximate location where the 1/4" hole is to be drilled.

With the evaporator box removed, you can actually see the drain tube.

Be sure to refer to TSB: 24-06-96