Praise be to Allah.
Zakaat al-fitr must be given in the form of food, and it is not permissible to give it in the form of cash.
But, if the poor will not accept food and ask for cash, it is permissible to give it in the form of cash in that case, and in that case one will be excused for not giving it in the form of food.
Shaykh Ibn Uthaymeen (may Allah have mercy on him) said:
With regard to one who knows that it must be in the form of food, but he gives it in the form of cash because it is easier for him, that is not acceptable. But in the example mentioned by the questioner, if we cannot find anyone who will accept food, i.e., there is no one who will accept the rice or dates or wheat, and they will not accept anything but cash, in that case we may give it in the form of cash. So we should work out the cash value of a saa of average quality food and give it to them.
End quote from Fataawa Noor ala al-Darb
And Allah knows best.
Reproduced from Islam QA