Does gastroscope break the fast?

Answer

Praise Be to Allah and Peace Be Upon His Messenger.

Referring to your question, most scholars agree that gastroscope breaks the fast. However, there are opinions:

The Hanafi school and many contemporary scholars see that it does not break the fast as it is not food or similar to food, nor does it stay or remain in the oral cavity.

Muslim World League decided that the followings do not break the fast; they mentioned gastroscope amongst them as long as no liquids or other substances enter the stomach. (The Muslim World League Journal: (10/2/453-455)

To sum up, if there are certain liquids, fats, or other substances that must be inserted in the stomach, it does break the fast; otherwise, it does not.