It is from the mercy of Allah and the easiness of the religion that we are allowed to break the fast if there is any danger, hardship or difficulty in it. Allah Says (what means): "...He (Allah) has chosen you and has not placed upon you in the religion any difficulty..."[Quran 22:7.8]
It is allowed for those who are (not chronically) ill and for travelers to break their fasts during Ramadan, but they must make up the days they missed. Allah Says (what mean): "[Fasting for] a limited number of days. So whoever among you is ill or on a journey [during them]-then an equal number of days [are to be made up]..." [Quran 2:184]
Mu'aath, may Allah be pleased with him, said: "Verily, Allah made the fast obligatory upon the Prophet by revealing (what means): "O you who believe, fasting is prescribed for you as it was prescribed for those before you ... and for those who can fast [but do not] there is a 'ransom' payment..." At that time, whoever wished to do so would fast and whoever wished not to do so would feed a poor person, and that was sufficient for them. After that, Allah revealed another verse (what means):"The month of Ramadan in which the Quran was revealed … Whoever is resident among you during this month is to fast." [By this verse,] fasting was established for those who were resident and healthy. A concession was made for the traveler and the sick, and the feeding of the poor by the elderly who could not fast was [left] confirmed." [Ahmad, Abu Daawood and Al-Bayhaqi]
If fasting during travel is not difficult, then it is better to fast. If fasting would be difficult then breaking the fast is better. Abu Sa'eed Al-Khudri, may Allah be pleased with him, said: "we used to travel for war expeditions with the Messenger of Allah during Ramadan. Some of us would fast and some of us would not fast, and the fasting person would not find fault with the one who was not fasting, and the person who was not fasting would not find fault with the person who was fasting. Then they thought that the person who had the strength would fast and that was better. And they thought that the person who felt weak would not fast and that was better." [Muslim]
If the person is ill during Ramadan, and is able to fast without difficulty, then he fasts. If he is unable then he breaks his fast.
If the ill person expects to recuperate from his illness, he waits until he recuperates and then he makes up for whatever days he did not fast. However, if he is not expected to recover, he breaks his fast and gives charity for each day that he does not fast. Allah Says (what means):"...And upon those who are able [to fast, but with hardship]-a ransom [as substitute] of feeding a poor person [each day]... " [Quran 2:184]
As for the elderly person who has reached an old age, at which he doesn't have the strength to fast, he may break the fast and give charity for every day that he did not fast. Ibn 'Abbaas, may Allah be pleased with him, said: "It was permitted for the very elderly man (or woman) to feed a poor person for every day (that he did not fast), and he did not have to make up for the days." [Ad-Daaraqutni and Al-Haakim]
Breaking the Fast without a legitimate excuse:
Regarding the one who intentionally breaks the fast by having sexual intercourse with his wife during the daytime in Ramadan, then he has committed a great sin and violated the sacredness of this month, and must make up the fast for that day. In addition, he is required to free a slave if it is possible to do so, if not, he has to fast two consecutive months and if he is unable to do so, then to he has feed sixty poor and needy people. The same is required of the wife as is required of her husband, if she freely consented (to having sexual intercourse). However, if she was forced, then nothing is required of her according to the predominant opinion of the scholars .
If one intentionally breaks his fast by eating or drinking without a legitimate excuse, then again he has committed a great sin and violated the sacredness of this month. Such a person has a severe threat awaiting him. Prophet Muhammad said: "Whoever breaks fasting of Ramadanwithout having a legitimate excuse or being ill, he cannot make up for that day, even if he undertakes a perpetual fast.” [Al-Bukhari] Imaams Ahmad, Ash-Shaafi’i, Sa'eed Ibn Al-Musayyib and Al-Sha'bi and others declared that one should sincerely repent and seek the forgiveness of Almighty Allah and make up the day later.
On the other hand, a group of Muslim scholars believe that expiation is required for breaking the fast of any day of Ramadan without a legal reason. They say, one should fast for two months consecutively or feed sixty poor people as well as to make up the day later with any of both forms of expiation.
Vomiting, if done deliberately, invalidates the fast, and necessitates making up for the fast. However, If vomit overcomes one and exits without one’s choosing, the fast is not nullified. -islamweb.net