Question: One day during Ramadaan I had some teaat Suhoor (pre-dawn meal before the Fast). I slept without washing my mouth. When I woke up, the taste of tea was still in my mouth. Do I have to make up for that day?
Answer: Your feeling of the taste of tea after waking up in the morning does not invalidate your Sawm (Fast), as you drank the tea before the break of the second dawn. Therefore, your Sawm is valid and you are not required to make up for that day... read more here.