There is no special dua to begin the fast, Niyah means intending by heart, it is not necessary to utter it by mouth.
Words regarding the niyah have not been narrated from the Prophet Mohammad Pbuh.
Zhahaba al-zama’ wa abtalat al-‘urooq wa thabata al-ajr in sha Allah
“Thirst is gone, the veins are moistened and the reward is certain if Allaah wills.”
Abu Dawud: 2357
8:24 PM
“I seek forgiveness from Allah for all my sins and turn to Him.”
Hasbun’Allahu wa Ni’mal Akeel
Allah is Sufficient for us and He is the Best Disposer of Affairs.
[ Al- Quran 3:173 ]
Allahumma Ballighna Ramadan
Oh Allah, let us reach the month of Ramadan.
[Mishkat al-Masabih 1369 ]
Allahumma la sahla illa ma jaaltahu sahla wa anta tajal ul-hazna idha shita sahla.
O Allah! Nothing is easy except what You have made easy. If you wish, you can make the difficult Easy.
[ Hisn al-Muslim 139 ]
Rabbana Faghfiırlana thunoobana wa kaffir Anna sayyi aatinaa wa tawaffana ma alabraar
Our Lord! Forgive us our sins and remit from us our evil deeds and make us die with the righteous.
[ Al-Quran 3:193 ]