Doubting whether or not dawn has broken and wanting to have Suhoor

Question: A man doubts whether or not dawn has broken and he wants to eat Suhoor (pre-dawn meal before the Fast), what should he do?

Answer: The basic principle is that as long as night remains, it is permissible for a Muslim to have food and the like. One should not abstain from food until the break of dawn, whether through observing or hearing a reliable Mu’ath-thin (caller to Prayer) announces the break of dawn... read more here.

Drinking while fasting after the dawn breaks

Question: An inquirer mentions in his question that sleep overwhelmed him one night in Ramadaan. He woke up being thirsty and the dawn broke, so he drank. What is the ruling?

Answer: If you are quite sure that the dawn broke and you drank intentionally, it is obligatory on you to make up for that day and ask Allaah (Exalted be He) for forgiveness... read more here.