What is the dua for breaking fast and when should it be recited?

The dua for breaking fast is "Allahumma inni laka sumtu wa bika aamantu wa 'ala rizq-ika aftartu" which translates to "O Allah, I fasted for You and I believe in You and I break my fast with Your sustenance." This dua should be recited right before breaking the fast at sunset.