Ordinary glass cups cannot be heated in an oven or microwave. The heat resistance of ordinary glass cups is not particularly good, and the temperature difference they can withstand is only about 60 degrees Celsius. Whether it is rapid heating or rapid cooling, it may cause the glass to burst. So don't put a regular glass in the microwave to heat it up.
Tempered glass cups without homogenization treatment pose a risk of self explosion and personal injury when used in ovens or microwaves. Tempered glass cups should not be heated in microwaves because they contain metal components and are fragile when heated. On the other hand, toxins may precipitate during heating, which is harmful to health.