The following dua (prayers) are recited at the beginning and end of the fast to indicate and affirm the intention of the fast.
A person’s intention when fasting, is to bring him/herself closer to Allah.
Dua (Prayer) at the Beginning of the Fast :
Wa bisawmi ghadinn nawaiytu min shahri ramadan
I intend to keep the fast for tomorrow in the month of Ramadan
Dua (Prayer) at the End of the Fast :
Allahumma inni laka sumtu wa bika aamantu wa alayka tawakkaltu wa ala rizq-ika-aftartu
O Allah! I fasted for You and I believe in You and I put my trust in You and I break my fast with Your sustenance