The doa at iftar is: 'Dhahaba az-zama'u wabtallatil-'uruqu wa thabatal-ajru insha'Allah' — The thirst has gone, the veins have been moistened, and the reward is confirmed, if Allah wills. This is the authentic sunnah doa for breaking the fast.
ذَهَبَ الظَّمَأُ وَابْتَلَّتِ الْعُرُوقُ وَثَبَتَ الْأَجْرُ إِنْ شَاءَ اللَّهُ
Dhahaba az-zama'u wabtallatil-'uruqu wa thabatal-ajru insha'Allah.
Meaning: The thirst has gone, the veins have been moistened, and the reward is confirmed, if Allah wills.
Source: Sunan Abu Dawud #2357Nabi (shallallahu alaihi wa sallam) said: 'There are three whose doa is not rejected: the fasting person until he breaks his fast, the just ruler, and the doa of the oppressed' (Sunan al-Tirmidhi 3598). The moment of iftar is thus one of the most powerful times for doa, and the fasting person should prepare their most important doa-doa for this moment.
ذَهَبَ الظَّمَأُ وَابْتَلَّتِ الْعُرُوقُ وَثَبَتَ الْأَجْرُ إِنْ شَاءَ اللَّهُ
When the Prophet (peace be upon him) broke his fast, he would say: 'Dhahaba az-zama'u wabtallatil-'uruqu wa thabatal-ajru insha'Allah.'