How is water getting in my car?!?!?

A very common problem occurs at some cars,

Cleaning the right side water drainage rubber at the right side of the roof will most probably solve the problem.

Sunroof hose is clogged

Weatherstripping needs to be replaced.

You have an open space, Either the door or the window. Use a hose to find out. Was the door ajar?  Weather stripping isn't too expensive & if you're careful, you can do it yourself. Was the door damaged? If so, go back to the repair shop.

You start by checking out the floor pan by crawling under the car. See any rust holes? If everything looks good under the car find out if the headliner is wet anywhere after the next time you wash the car or drive in the rain. If you have a sunroof open it and make sure the 4 drain tubes for the sunroof tray are free of debris.

Leak check the right side windows with the garden hose.  The weather striips in the frame and window might need replacement.

I would spray with more water, since that's what a heavy rain and a car wash is.  That happened to the left side of my trunk the first time I took it to a car wash, fortunately I had removed everything from there.

window seals are Notorious for leaks Have you checked your Rear wheel wells in the Boot/Trunk

My Mercedes Benz had a rubber tube to take water from the Boot/Trunk Rim and it had a Hole in it Filled up the Rear seat well and the Boot

Perhaps, there is a hole in the undercarriage.  Is it an old car?  Has it been through snow & salt?  Are there signs of rust?  Take it to a garage and have them put it up where you can see the bottom.   It might very well have a hole.

Have you looked under the car for a rust hole?