Why does the ford fiesta have water in the spare wheel well?

If You have water in the spare tire well of Your Ford Fiesta that is usually a sign that there is a problem with either the window or the rear air flow vents. The trunk is designed to be vented out so that exhaust gasses do not get trapped in it, and if there is a problem with those lines they can allow water back into the trunk. Your trunk also has a set of gutters that are designed to move water from the rear window down and out of the vehicle. If something is wrong with these gutters or the rear window then that will also allow water into Your trunk. The water just happens to pool in the spare tire well because that is the lowest point in the trunk.