Firstly:

Zakaat al-fitr is required from a man on his own behalf and on behalf of those on whom he is obliged to spend, such as his wife, child and so on, because of the report narrated by al-Daaraqutni and al-Bayhaqi from Ibn 'Umar (may Allaah be pleased with him), that the Prophet SAWS (Peace And Blessings Of Allaah Be Upon Him) said: "Pay zakaat al-fitr on behalf of those whom you support." But this is a da'eef (weak) hadeeth, which was classed as such by al-Daaraqutni, al-Bayhaqi, al-Nawawi, Ibn Hajar and others.

See: al-Majmoo' (6/113) and Talkhees al-Habeer (2/771).

The scholars of the Standing Committee for Issuing Fatwas said: Zakaah al-fitr must be paid on behalf of oneself and everyone on whom one is obliged to spend, including one's wife, because he is obliged to spend on her. End quote.

Fataawa al-Lajnah al-Daa'imah li'l-Ifta (9/367).

Secondly:

If a woman has been given a revocable divorce, then she comes under the same rulings as a wife; she is entitled to the same maintenance and accommodation, so long as her 'iddah has not yet ended. Payment of zakaat al-fitr is connected to spending; so long as the husband is obliged to spend on the wife who has been given a revocable divorce, then he also has to pay zakaat al-fitr on her behalf.

Al-Nawawi said in al-Majmoo' (6/74): Our companions said: He has to pay zakaat al-fitr on behalf of his revocably divorced wife just as he has to spend on her. End quote.

Ibn Yoosuf al-Mawaaq, who is one of the Maalikis, said in al-Taaj wa'l-Ikleel (3/265): If he divorces a wife with whom he has consummated the marriage, giving her a revocable divorce, then he is obliged to spend on her and give zakaat al-fitr on her behalf. End quote.

Some scholars are of the view that the husband does not have to give zakaat al-fitr on behalf of his wife, rather it a duty that she must fulfil herself. This is the view of Imam Abu Haneefah (may Allaah have mercy on him) and was favoured by Shaykh Ibn 'Uthaymeen. See the answer to question no. 99353.

The husband should do that which is on the safe side and discharge his duty by paying zakaat al-fitr on behalf of the wife to whom he has given a revocable divorce, especially as zakaat al-fitr is a small amount and it is not usually difficult for the husband to pay it.

And Allaah knows best.