2000 toyota tundra water leak passenger side under dash

It may be leaking through the evaporator intake vent... There are no TSB's for any kind of water leak in 2000, you may just have to start disassembling stuff until you find where the water is originating from. It's probably something stupid, but check any rubber grommets, harnesses, the evap intake port, anything you can see that goes into where you can get it to leak from.