Most of action movies involve tremendous amounts of explosions and shattered glass. I remember watching Die Hard (1988) and the amount of broken glass made me wonder, what was it made of to keep actors safe?
It's not actually glass...
Originally, they used a product called "Sugar glass" or "candy glass".
Sugar glass (also called candy glass, edible glass, and breakaway glass) is a brittle transparent form of sugar used to simulate glass in movies, photographs and plays. It is much less likely to cause injuries than real glass, and it easily breaks convincingly, making it an excellent choice for stunts. Sugar glass is also used to make sugar sculptures. Because sugar glass is hygroscopic, it must be used soon after preparation, or it will soften and lose its brittle quality.
It's incredibly easy to make, taking no special skill (Practice for clarity and equipment to make large pieces aside).
However, the sugar absorbs moisture, it isn't very stable, so they have modern substitutes made from brittle plastics. They are still very easy to break but they don't suffer from deterioration over time the way that sugar does.
Q: Is it made of sugar?
A: Breakaway Glass is made of a mixture of plastics, not sugar.
Also, because it's not sugar, it can be used for vessels and jars, so it can hold liquids, at room temperature.
Note that there is still some risk. You're not as likely to be injured by breakaway glass as real glass but you can still get hurt, so stunts people are still very cautious around these products.