Tears or sweat going down the throat. If just a drop or two went down and no salty taste is felt in the throat, the fast will not break. However, if it was a lot, or a little but the taste was felt, it will break.

اذا دخل الدمع فى فم الصائم ان كان قليلا نحو القطرة او القطرتين لا يفسد صومه لان الإحتراز عنه غير ممكن. وان كان كثيرا حتى وجد ملوحته فى جميع فمه وابتلعه فسد صومه وكذا الجواب فى عرق الوجه

ِامى ص 178 / 3 أحكام

Extracted from A Gift for Ramadhan, Page 59.

A Gift For Ramadhan – New 3rd Revised Edition