It is not permissible to drink after the break of dawn.

If you believe that the Athan is called before the actual break of dawn, you can drink. But if you don’t know, you shouldn’t drink.

I usually have a glass of water as soon as i hear fajr adhaan.just to be well hydrated and to gulp down any food left in my mouth. is my fast valid. if yes then plz give me some proof or a link to which i can also show my friends. if no then ,will my previous fast be valid and accepted?