This question was put to Shaykh Muhammad ibn ‘Uthaymeen (may Allaah have mercy on him), who said:
“Du’aa’ should be made before iftaar (breaking the fast), at Maghrib, because this combines weakness and humility, and because he is still fasting. All of these are means of having one’s du’aa’ answered. After breaking the fast, one is relaxed and happy, and may become negligent. But there is a hadeeth from the Prophet (peace and blessings of Allaah be upon him) which, if it is saheeh, shows that the du’aa’ may be made after breaking the fast. It said: ‘Thirst has gone, the veins are moist, and the reward is assured, if Allaah wills.” (Narrated by Abu Dawood; classed as hasan by al-Albaani in Saheeh Sunan Abi Dawood, 2066). This can only mean after breaking the fast. Similarly it was narrated that some of the Sahaabah said: “ O Allaah, for You I have fasted and with Your provision I have broken my fast.”
So you may pray to Allaah and say whatever du’aa’ you think is suitable.