بسم الله الرحمن الرحيم
Q: A man, traveling and fasting, during Ramadan intends to break his fast, thereafter he doesn’t find anything with which to break it, so he modifies his intent and completes his fast. What is the validity of his fast?
A: His fast is not valid and binding upon him is another day, due to him -when intending to break the fast- broke his fast. As for if he had said, “If I find water then I’ll drink and if don’t then I’ll remain fasting” yet doesn’t find water, then this fast is valid because he did not intend to break it. On the contrary he attached (i.e. stipulated upon himself) breaking it to the presence of something (with which to break it) and if that thing isn’t present then he would remain upon his first intent.
Source: فتاوى في أحكام الصيام