Answered by Shaykh Amjad Rasheed
What is the recommended du’a to say when one is ending one’s fast what and does one say it after or before eating?

It is sunna for one fasting, at the time of eating, to make dua’ and say,
اللهم لك صمتُ ، وعلى رزقك أفطرتُ
“O Allah, I have fasted for you and I am eating from the sustenance which you have given me.”
This has been related by Abu Dawud, by a good chain and he also related an addition [s. to this du`a],
ذهب الظمأ وابتلت العروق وثبت الأجر إن شاء الله تعالى
“Thirst is gone ..and the reward is affirmed, if Allah, Most High has willed.”
And there are other narrations.
As for the time of this du`a, what our imams have said is that it is said right after eating, not before, so one says it after one has eaten. It says in the Tuhfa with the Minhaj, (3:425), “(and) it is sunna (that one say when ending one’s fast), i.e., immediately after (Allahumma laka ..etc).
And Ramli related the same thing in the Nihayah and so did al-Khatib in the Mughni.
Amjad Rasheed
[Translated by Sr. Shazia Ahmad]