Duaa-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)