What type of journey on which breaking the fast is permissible?
The distance of the journey for which it is permissible to shorten the obligatory prayers and to break the fast is approximately 83 kilometres. Some scholars, however, do not specify a distance for the journey. They maintained that whatever is commonly understood as a journey amongst people constitutes a journey in Islam.
The Messenger of Allah (PBUH), used to shorten the prayers if he traveled 3 faraasikh (which is equal to 9 miles). If the journey is undertaken for impermissible purpose, then shortening the prayers and breaking the fast are not allowed because any journey that is undertaken for evil purposes does not deserve (such a) concession.
Some Muslim scholars, however, do not differentiate between a journey undertaken for an evil purpose and one undertaken for a permissible purpose because of the generality of the evidence surrounding the issue. Allah knows best.