Passenger's side? Could be a leaking heater core
Antifreeze will be leaking in the floorboard on the passenger side, there will be a smell of antifreeze through the vents.
heater core is leaking.
Probably a leaking heater core.
bad door seals
This would be caused by a leaking heater core, or a leak in the plumbing associated with it.
If that water is engine coolant, the heater core is leaking.
your heater core is leaking i would replace it.
Because the air conditioner is running.
The heater core (a small radiator for your heat) is leaking, I would suggest a new heater core as they are about as cheep to replace as they are to repair.
Either the heater core is leaking or you have a leak at the windshield or the cowl. If the fluid tastes sweet it is coolant and your heater core is leaking.
Possibly air conditioner drain hose is clogged