Water spill inside on the passenger's side?

Hello,

When you notice the water, was it raining?
If it leaks in rain then you could have a windshield or window seal that is leaking.

If you notice water without any rain, then it could be leaking from the heater core.
Is there a sweet smell to the fluid?
If so then it is coolant.
In order to access the heater core you will have to remove part of the dash.

https://youtu.be/SNRb6pSwYuU

I have attached diagrams for the heater core.

Please let me know of any questions.

Thank you.