Does drinking water and juice upon waking invalidate the fast due to severe sore throat?

If the mentioned illness is one that permits breaking the fast, then there is no sin upon whoever breaks the fast because of it. And it is obligatory for him to make up that day before the advent of the next Ramadan (definition), due to His Almighty saying: "So whoever among you is ill or on a journey, then [he must make up] an equal number of other days." As for refraining from eating and drinking for the rest of the day after the excuse is gone, there is a difference of opinion on that, but the more cautious approach is to refrain.