Things that invalidate the fast are called 'Mufattirat al-Saum' in Arabic. In the Quran, they are generally categorised into three things.
1. Eating
2. Drinking
3. Sexual intercourse
The verse referring to them is as follows:
"So now, you can have sexual intimacy with you and seek what Allah has destiner for you and eat and drink until the white thread of the dawn becomes distinct from the black thread; then complete the fast up to the night." (Surah Al Baqara: 187)
It is for this reason these 3 are called "Mufattirat Thalatha" (the three breakers of the fast).
۔۔۔۔۔۔۔۔۔۔۔۔۔۔۔۔۔۔۔۔۔۔۔
دلائل:
الموسوعۃ الفقہیۃ الکویتیۃ: (289/5، ط: دار السلاسل)
أجمع العلماء على أن من جامع أو استمنى أو طعم أو شرب عن قصد، مع ذكر الصوم في نهاره فقد أفسد صومه، لقوله تعالى: {فالآن باشروهن وابتغوا ما كتب الله لكم وكلوا واشربوا حتى يتبين لكم الخيط الأبيض من الخيط الأسود من الفجر}
Allah the Almighty knows best
Issued by Darul ifta Al-Ikhlas, Karachi.