What Are the Sunnahs of Fasting?
Question

What are the Sunnahs of fasting that the fasting person is encouraged to uphold?
Praise be to Allah.Reward of fasting
Fasting is one of the greatest acts of worship, and the reward of the one who fasts, seeking thereby the reward of Allah , is not known to anyone except Allah.
The Prophet (blessings and peace of Allah be upon him) said: “Allah, may He be glorified and exalted, said: ‘Every deed of the son of Adam is for him, except fasting. It is for Me and I shall reward for it.’” (Narrated by al-Bukhari, 1904,  and Muslim, 1151)
The Ramadan fast is one of the pillars of Islam , and the Muslim must pay attention to preserving his fast, whether it is obligatory or supererogatory, so that Allah may bestow upon him this abundant reward. 
Sunnahs of fasting
There are many Sunnahs with regard to fasting , of which we will mention some: 

It is Sunnah, if someone reviles the fasting person or tries to fight him, to respond to his mistreatment with kindness and to say: “I am fasting .” 
It is Sunnah for the fasting person to eat Suhur, for Suhur is a blessing (barakah). 
It is Sunnah for him to hasten to break the fast , and to delay Suhur . 
It is Sunnah for him to break the fast with fresh dates; if he cannot find any, then he should break his fast with dried dates. If he cannot find any dates, then he should break his fast with water. 
It is mustahabb for the fasting person to say, when he breaks his fast: “Dhahaba al-zama -u wa abtalat al-‘uruqu wa thabata al-ajr in sha Allah (Thirst is gone, the veins are moistened and the reward is certain if Allah wills).”. 
It is mustahabb for the fasting person to offer a great deal of supplication (du`a), because the Prophet (blessings and peace of Allah be upon him) said: “There are three whose supplication will not be rejected: the just ruler, the fasting person until he breaks his fast, and the supplication of one who has been wronged.” (Narrated by Ahmad (8043); classed as sahih by the commentators on al-Musnad, taking into account all its isnads and corroborating evidence.) 

An-Nawawi (may Allah have mercy on him) said: 
“It is mustahabb for the fasting person to offer supplication whilst fasting with regard to what concerns him of the Hereafter and of this world, for himself, for those whom he loves, and for the Muslims.” (Al-Majmu‘, 6/375) 

If it is a Ramadan fast, then it is mustahabb to do the following: 


To sit in the mosque to read Quran and remember Allah (dhikr)
To observe i`tikaf in the last ten days
To pray Tarawih
To give a great deal of charity and do a great deal of good deeds
To study the Quran. 

Al-Bukhari (6) and Muslim (2308) narrated that Ibn `Abbas said: The Messenger of Allah (blessings and peace of Allah be upon him) was the most generous of people, and he was at his most generous in Ramadan when Jibril used to meet him. He would meet with him every night in Ramadan and revise the Quran with him, and the Messenger of Allah (blessings and peace of Allah be upon him) was more generous in doing good than the blowing wind. 
And the fasting person should not waste his time in doing things that are of no benefit or no use – and may adversely affect his fast – such as sleeping a great deal, joking a great deal, and so on. He should not make eating different kinds of food and drink his main concern. All of that will prevent him from doing a great deal of good deeds whilst fasting. 
And Allah knows best.