Assalamualaikum warahmatullahi wabarakatuhu.
If one swallowed water at the time of wudhu unintentionally, then will the fast break?
بِسْمِ اللهِ الرَّحْمنِ الرَّحِيْم
In the name of Allah, the Most Gracious, the Most Merciful
Yes, if one swallowed water at the time of wudhu unintentionally, while remembering he/she is fasting, then his/her fast will be broken.
Only Allah knows best
Written by Alimah Sumeyye Sofu
Checked and approved by Mufti Mohammed Tosir Miah
Darul Ifta Birmingham
 Raddul Muhtar p.374 v.3 Darul alimil kutub