Dua for breaking the fast in Islam:

"اللهم إني لك صمت وبك آمنت وعلى رزقك أفطرت"

Translation: "O Allah, I fasted for You and I believe in You and I break my fast with Your sustenance."

Arabic: ذهب الظمأ وابتلت العروق وثبت الأجر إن شاء الله
Transliteration: ḏahaba aẓ-ẓamaʾu wa-ibtalat al-ʿurūq wa-ṯabata al-ajru ʾin šāʾ Allāh
Translation: The thirst has gone, the veins are moistened, and the reward is confirmed, God willing