If it's the front passenger side ,I would say your heater core is leaking .
Windshield seal? Lower door seal? Hole in floor ?
Fluid on the passenger side floor is one of two things. Either you have a water leak from outside, as in a windshield leaking, condenser drain line stopped up and leaking into the car, or the heater core is leaking. Taste the fluid. If it taste sweet, it is coolant and the heater core needs replacing.
Heater core has failed.
clogged or damaged catalytic converter
Heater core
It could be the heater core leaking.
most likely cause is your heater core leaking
Leak in heater core
The ac drain is plugged. The drain hose is on the firewall on the lower passenger side. ...that, or your heater core is leaking.
It fastens to a pass through stud at the passenger floor.
Heater core may be leaking Door seal? Windshield seal?
It could be a door seal or more likely the windshield is leaking.