When Is It Forbidden for a Traveller to Break the Fast?
Question

When is it forbidden for a traveller to break the fast? Please explain why.
Praise be to Allah.Fasting while travelling: Permissible?
The Quran and Sunnah, and the consensus of the ummah, indicate that a person who is travelling during the day in Ramadan is allowed not to fast . Allah says (interpretation of the meaning): 
“and whoever is ill or on a journey, the same number [of days which one did not observe Sawm (fasts) must be made up] from other days” [al-Baqarah 2:185]
The jurists (may Allah have mercy on them) stated that the traveller who is allowed not to fast is one who is travelling the distance at which it becomes permissible to shorten the prayers, and is travelling for a permissible purpose. 
If a person is travelling a distance shorter than that at which it becomes permissible to shorten the prayers or he is travelling for sinful purposes, then it is not permissible to shorten the prayers . The same applies to one who travels in order to be able to break the fast : it is haram for him to travel and to break the fast. 
How many miles do you have to travel to break your fast?
According to the majority of scholars, the distance at which it becomes permissible to shorten the prayers is four stages, which is equivalent to approximately 80 kilometers. Some scholars are of the view that it cannot be reckoned by distance, but is rather what the people describe as travelling. 
Can you break your fast if you are traveling for sinful purposes?
The view that the one who is traveling for sinful purposes is not allowed to break his fast or avail himself of any of the other concessions granted to travellers, such as shortening the prayers, is the view of the Malikis, Shafi`is and Hanbalis. (See al-Mughni, 2/52) 
They gave the reason for that as being that being allowed to break the fast (whilst travelling) is a concession, and the one who is travelling for sinful purposes does not deserve any concession. Some of them quoted as evidence the verse in which Allah says (interpretation of the meaning): 
“But if one is forced by necessity without willful disobedience nor transgressing due limits, then there is no sin on him.” [al-Baqarah 2:173]
The point here is that Allah has not permitted the eating of dead meat to those who are willfully disobedient or who transgress the limits, because they are sinners. They said: The one who is willfully disobedient is the one who rebels against the ruler, and the one who transgresses the limits is the one who rebels against society and commits highway robbery (like a bandit). 
The Hanafis are of the view that the one who travels for sinful purposes is allowed to break the fast, shorten the prayers and so on. This is also the view favoured by Ibn Taymiyah (may Allah have mercy on him).  (See al-Bahr al-Raiq, 2/149; Majmu’ al-Fatawa, 24/110 )
They did not agree with the majority’s use of this verse as evidence. They said: The one who is willfully disobedient is the one who seeks haram food despite the fact that he is able to obtain halal food, and the one who transgresses the limits is the one who takes more than he needs. 
Can you break your fast if you travel just to break the fast?
With regard to the one who travels in order to break the fast, he is trying to find ways around the rulings of shari’ah, so he should be punished by being denied the concession. 
It says in Kashshaf al-Qina’, 2/312, which is a Hanbali book: 
“But if he travels in order to break the fast, they both become haram for him, i.e., travelling and breaking the fast, because there is no reason for his travelling except breaking the fast. It is haram for him to break the fast because he has no legitimate reason to allow him to do that, and it is haram for him to travel because it is a means to break the fast in a haram manner.” 
When can a traveller start breaking his fast?
The traveller does not have the right to break his fast except after he has left behind the built-up area of his city or village. It is haram to break his fast before that, because he is still a non-traveller in that case. 
When is it haram for a traveller to break his fast?
Based on this, it is haram for a traveller to break his fast in several cases, including the following: 

When he is travelling but the distance does not reach the distance at which it becomes permissible to shorten the prayers.
When his journey is not permissible according to the majority of scholars.
When he is travelling in order to break the fast.
When he is travelling and wants to break the fast before leaving the houses of his village or city.
There is a fifth case in which it is haram for a traveller to break the fast according to the majority of scholars. That is when he is staying in the place to which he has traveled for more than four days . Other scholars say that the concessions of travel apply to the traveller no matter how long he stays.

And Allah knows best.