It is extremely difficult to break the windows in modern cars using a blunt object such as a hand or a foot. It is also possible to injure yourself. The best way to break a window (and you'll find that this method is extremely easy) is to use a ballpoint pen, screwdriver, or other object with a strong, pointed tip. Smash the tip of the pen (or other object) into the middle of the window with as much force as you can, and the window will break, even if there is water on the other side of it. Don't even think about trying to break the windshield'll never succeed. Break one of the side windows.