Breakaway Glass
In movies, when someone needs to get thrown through a window, or have a bottle smashed over their head, filmmakers use breakaway glass.
In older movies (as well as more recent movies with a lower budget), sugar glass was the method of choice. Sugar glass is cheap and relatively simple to make, you can even make it in your own kitchen! It’s just sugar dissolved in water, heated up and mixed with corn syrup or glucose, and sometimes some cream of tarter added in. This is easier to shatter than real glass, and much less likely to injure a stunt performer.
Sugar glass can be very effective, but it has to be used soon after it’s created. Sugar is hygroscopic, meaning that it attracts water from the environment, which causes it to soften. Because of this, many modern movie makers prefer a Piccotex/Piccolastic mix.