my car collects water on the passenger side floors when it rains
Either windshield or window on door is probably leaking ( runs down the inside of door and out the bottom) Get some Red and green food coloring at the bottom of the windshield put one color at the bottom of the door window put the other color ... next time it rains take a paper towel and blot the floor ... that should give you a direct of where to look
Possibly a clogged sunroof drain. Here is a video link that shows how to clean them. https://www.youtube.com/watch?v=1CiqO11FtvQ
I wouldnt use the food coloring it might stain your carpets.