That is OK, but it is preferable not to break the fast, except in cases of necessity, and you should make up that day. But so long as a person is able to complete his fast, it is not permissible for him to break it. But if an accident happens far away, for example, and the sun is burning down in the summertime, and you go there to rescue the injured or put out a fire, and you feel thirsty and are afraid that your thirst will affect you adversely, then in sha Allaah it is OK to break your fast. Allaah says (interpretation of the meaning):
“So keep your duty to Allaah and fear Him as much as you can” [al-Taghaabun 64:16]
“Allaah burdens not a person beyond his scope” [al-Baqarah 2:286]And the Prophet (peace and blessings of Allaah be upon him) said:
“If I command youto do a thing, do as much of it as you can.” (Narrated by Muslim, no. 1337; al-Nasaa’i, 5/110).This applies so long as no travel is involved; if the matter involves travelling, then it is unconditionally permitted to break the fast. And Allaah knows best.