Is the fast valid if the taste of a throat freshener reaches one's throat, and one gargles and rinses with water, while doubting whether the water was swallowed?

All praise is due to Allah, and may peace and blessings be upon the Messenger of Allah, and upon his family and companions. To proceed:

The presence of perfume taste in the throat does not invalidate the fast. Doubting whether something from the gargle water was swallowed does not invalidate the fast, and the default is that the fast is valid. Therefore, your fast is valid and nothing is required of you. And Allah knows best.