Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him) narrates that we used to give one sa' of dates, or one sa' of barley, or one sa' of raisins, or one sa' of cheese, or one sa' of Hijazi barley as Sadaqat al-Fitr.
Hadith Referenceصحيح ابن خزيمه / جماع أبواب صدقة الفطر فى رمضان / 2414