Things that break the fast are eating, drinking and intercourse. Besides, people that are ill or on a journey have the permission not to fast. They can also break their fasts for taking medication. Your friend should fast only for one day. The Glorified Allah commands:
“Fast for a certain number of days. Whoever among you is sick or on a journey, should fast the same number some other days (…)” (Al-Baqarah 2/184)
“The month of Ramadan in which was revealed the Qur’an, a guidance for mankind and clear signs of right path. It lets discern right from wrong. So whoever of you sees that month, should spend it in fasting. Whoever is sick or on a journey, should fast the same number some other days. Allah desires ease for you, and He does not desire for you difficulty. He facilitates for you that you may complete the number of Fast days and glorify Allah for He has shown you the right path, and perhaps you will be grateful.” (Al-Baqarah 2/185)
As narrated from Jabir ibn Abdullah, the Prophet (p.b.u.h.) was on his way to Mekkah in the year of victory. He and his companions were fasting when they arrive at a place called Kurau’l-Gameem. It is said to the Prophet; “Fasting tires the people; they keep on by looking at you”. The Prophet asked for a cup of water afternoon and drank it in front of people’s eyes. Some of them broke their fasts when they see this, some of them continued fasting. When he’s been informed that some of the companions continue fasting, the Prophet said; “They don’t obey, they are defiers”. (Muslim, Siyam, 90 (1114); Tirmidhi, Sawm, 18.)
This hadith are not contrary to the verse that commands as the fasting is better in journey and illness. The hadith declares that one should not continue fasting when he is in a position of getting harmed by it. People that insist on fasting while in this kind of position are considered as defiers. As the considered verse commands; for ones that are not in a position of getting harmed by it, surely fasting is better.