Deep grief has a way of invading even the most basic elements of human survival. When a person is overwhelmed by sadness, the simple acts of eating and drinking are no longer sources of nourishment, but become painful reminders of suffering.
The primary approach among commentators is that consuming ashes is a powerful metaphor for intense trouble and sorrow [רד״ק, אבן עזרא, מצודת דוד, מאירי]. The weight of sadness completely robs a person of the ability to enjoy food, making the bread in their mouth taste like dry ashes. However, others understand this as a literal reality of extreme mourning or living through destruction [אלשיך, ביאור שטיינזלץ]. In this view, ashes were not merely a symbol or something to dip bread into as a sign of grief; rather, the ashes became the actual, primary food. This literal interpretation is supported by a tradition regarding King David. During the years when the Holy Spirit departed from him, he wept so much that he consumed equal amounts of ashes and bread [מנחת שי].
This profound sadness extends to drinking as well. Every type of beverage becomes mingled with tears [רש״י, רד״ק, מצודת ציון]. As the mourner tries to drink, tears fall directly from their eyes into the cup, blending the liquid with their crying [מצודת דוד]. This act mirrors the common practice of diluting wine with water, but here the drink is cut with the bitter waters of affliction [רד״ק]. The sorrow is so complete that it creates a striking image of a cup filled with three parts of tears for every one part of actual drink [אלשיך].