Assalamu alaikum warahmatullahi wabarakatuh,
Rasulullah SAW obligates us to pay Zakat Fithr to people on the month of Ramdhan for one sha’ of date palm or sya’ir, such as to every free people, slaves, men and women of the Muslims. (Hadith Narrated by Jamaat except Ibn Majah from the hadith of Ibn ‘Umar).
So from the above arguments, it is clear that the charity is associated with Ramadhan. Zakat Fitr is actually preferred to be given on the night of 1 Shawal until Eid al-Fitr prayer, as the following hadith.
Ibn `Umar said that Rasulullah SAW obligates us to pay Zakat Fitr for 1 sha’ of date palm or one Sha’ of wheat flour (sya’ir), for any servant or master, male or female, children or adults of Muslim. And orders to be accomplished before the people finish the prayer. (Hadith Narrated by Muttafaq ‘Alaihi).
As a word of the Prophet Muhammad: “Feed them sufficiently today.”
So the essence of Zakat Fitr to make sure that no one is hungry on that day (day of Ied al-Fitr) because of live in a poverty. Anyway, all the poor people can eat and do not have to fast on that day. Even Allah has prohibit to fast on that day.
About the portion and kind of the food, depends on each country. If you look at the hadith of Prophet SAW, the kind and portion of food are accorded to the people custom of Medina. The people in Medina eat date palm or wheat flour as their food staples (the food which is needed to makes people do not starve and hungry).
Then the mujtahids (moslem scholars) in our country are also trying to convert the food needed as our nation’s food staples, such as rice. Certainly, there are differences of opinion as to convert them. For example, someone says that one sha ‘dzabib, date palm, hinthah, sya’ir or ‘athiq equal to 2, 176 kg. But someone also count them into 2, 5 kg.
There was even a measure by volume not by weight, so that it becomes 3, 5 liters of rice. Because according to them, the size of 1 sha’ is not a measurment of weight but the size of the volume.
In short, the food was enough to make someone does not starve in the day, it is the feast of Fitr. (Ahmad Sarwat, Lc/rumahfiqih.com)
See Also: Should NGO Pay Zakat?