Is It Haram to Break Your Fast with No Excuse?
Question

I do not fast. Will I be punished on the Day of Resurrection?
Praise be to Allah.Fasting is one of the pillars of Islam
Fasting in Ramadan is one of the pillars on which Islam is built . Allah tells us that He has prescribed it for the believers of this ummah [nation], as He prescribed it for those who came before them. Allah says (interpretation of the meaning): 
“O you who believe! Observing As-Sawm (the fasting) is prescribed for you as it was prescribed for those before you, that you may become Al-Muttaqun (the pious.” [al-Baqarah 2:183] 
“The month of Ramadan in which was revealed the Quran, a guidance for mankind and clear proofs for the guidance and the criterion (between right and wrong). So whoever of you sights (the crescent on the first night of) the month (of Ramadan i.e. is present at his home), he must observe Sawm (fasts) that month, 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. Allah intends for you ease, and He does not want to make things difficult for you. (He wants that you) must complete the same number (of days), and that you must magnify Allah [i.e. to say Takbir (Allahu Akbar: Allah is the Most Great)] for having guided you so that you may be grateful to Him.”[al-Baqarah 2:185]
Al-Bukhari (8) and Muslim (16) narrated that Ibn ‘Umar (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings of Allah be upon him) said: “Islam is built on five (pillars): the testimony that there is no god but Allah and Muhammad is the Messenger of Allah; establishing prayer; paying zakah; Hajj; and fasting Ramadan.” 
Is t haram to break your fast?
Whoever does not fast has abandoned one of the pillars of Islam, and is committing a grave major sin. Indeed some of the salaf were of the view that he is a disbeliever and apostate – we seek refuge with Allah from that. 
Abu Ya’la narrated in his Musnad from Ibn ‘Abbas (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) said: “The bonds of Islam and the bases of religion are three, on which Islam was founded. Whoever gives up one of them becomes a kafir thereby and it is permissible to shed his blood (under strict conditions within an Islamic state under the orders of the ruler): the testimony that there is no god but Allah, the prescribed prayers and fasting Ramadan.” 
This hadith was classed as sahih by al-Dhahabi, and as hasan by al-Haythami in Majma’ al-Zawaid, 1/48, and by al-Mundhiri in al-Targhib wa’l-Tarhib, no. 805, 1486. Classed as da’if by al-Albani in al-Silsilah al-Da’ifah, no. 94.  
Al-Dhahabi said in al-Kabair, p. 64. 
Whoever does not fast in Ramadan without being sick or having any other excuse that allows him not to fast is more evil than the adulterer or drunkard, indeed they doubted his Islam and thought that this was heresy. 
Punishment of those who do not fast 
A sahih report which warns against not fasting was narrated by Ibn Khuzaymah (1986) and Ibn Hibban (7491) from Abu Umamah al-Bahili who said: I heard the Messenger of Allah (peace and blessings of Allah be upon him) say: “Whilst I was sleeping two men came to me and took me by the arm and brought me to a cragged mountain. They said, ‘Climb up.’ I said, ‘I cannot.’ They said, ‘We will make it easy for you.’ So I climbed up until I was at the top of the mountain. Then I heard loud voices. I said, ‘What are these voices?’ They said, ‘This is the howling of the people of Hell.” Then I was taken until I saw people hanging by their hamstrings, with the sides of their mouths torn and blood pouring from their mouths.’ I said, ‘Who are these?’ He said, ‘These are people who broke their fast before it was time.’” (Classed as sahih by al-Albani in Sahih Mawarid al-Zam’an, no. 1509)
Al-Albani (may Allah have mercy on him) said: “This is the punishment of those who fasted then broke the fast deliberately before the time for breaking the fast came, so what about those who do not fast at all? We ask Allah to keep us safe and sound in this world and in the Hereafter.” 
Advice for those who do not fast
Our advice to the brother who asked this question is to fear Allah and to beware of His wrath, vengeance and a painful punishment. He should hasten to repent to Allah before the destroyer of pleasures that splits people apart [i.e., death] takes him unaware. 
Today there is action and no reckoning, but tomorrow there will be reckoning and no action. Note that whoever repents, Allah will accept his repentance, and whoever draws closer to Allah one hand span, Allah will draw closer to him one cubit. For Allah is Most Generous, Forbearing and Most Merciful, as He says (interpretation of the meaning): 
“Know they not that Allah accepts repentance from His slaves and takes the Sadaqat (alms, charity), and that Allah Alone is the One Who forgives and accepts repentance, Most Merciful?” [al-Tawbah 9:104]
If you try fasting and find out how easy it is and what comfort it brings and how close it brings you to Allah, you will never give it up. 
Think about what Allah says at the end of the verses on fasting (interpretation of the meaning): 
“Allah intends for you ease, and He does not want to make things difficult for you.” [al-Baqarah 2:185]
The phrase, “so that you may be grateful to Him” shows that fasting is a blessing for which we must give thanks. Hence some of the salaf used to wish that the whole year was Ramadan. 
We ask Allah to help you and guide you, and to open your heart to that which will bring you happiness in this world and in the Hereafter. 
And Allah knows best.