Prophet (SAW)'s Prayers When breaking fast

Recite:

اللَّهُمَّ لَكَ صُمْتُ وَعَلَى رِزْقِكَ أَفْطَرْتُ

"O Allah, I have fasted for You and from the sustenance given by You, I break the fast". (Abu Dawood)

Alternate dua

اللَّهُمَّ إِنِّي أَسْأَلُكَ بِرَحْمَتِكَ الَّتِي وَسِعَتْ كُلَّ شَيْءٍ أَنْ تَغْفِرَ لِي ذُنُوبِي

"O Allah, I seek by your mercy which encompasses everything, that You forgive my sins". (Hisnul Hasin)