I have liquid leaking on the passenger's side floorboard.
The AC has a drain on the passenger side that if it gets clogged with debris then the AC water could back up into the passenger floor. Another issue could be the sunroof drains are getting clogged and could leak water in heavy rain conditions into the passenger area. The last problem could be coolant leaking from the heater core. This would be coolant though. The other two would only be water. I would recommend having a mechanic, like the certified ones at YourMechanic, come and check it out for you to see what is causing the problem.