Any time it rains hard the rear doors collect water. Enough you can hear it sloshing around while driving. Depending on how much rain, up to half a gallon. Easy enough to get out by removing one of the weather stripping clips on the bottom of the door, let it drain and replace. Guess it is coming in through the window trim.

Anybody else have this issue and luck fixing?

 

There should be drain holes in the bottoms of the doors . Clean them out .

 

After you clean out the drain holes, trim the weather strip to allow them to drain better.