In times of extreme crisis, the deepest impact is often felt by those who appear to be the strongest and most protected in society. A devastating state of deprivation will cause the youth of the nation to completely collapse. This collapse is a state of extreme weakness, an exhaustion of the soul that leads to a loss of sensation and the fading away of the spirit [רש״י, מצודת ציון, רד״ק].
The underlying cause of this fainting is a profound thirst, though commentators offer different perspectives on its exact nature. One approach understands this as a literal, physical lack of water that will strike on the day of disaster when the people are led into exile [מצודת דוד]. The severity of this drought is absolute. Even delicate young women, who are typically protected and provided for during times of shortage, will be left with nothing to drink. Similarly, robust young men, who can usually endure physical hardship, will completely lose consciousness [ביאור שטיינזלץ]. This physical devastation operates on a principle of divine justice. The youth will suffer from this physical thirst specifically because they lack a thirst for the word of God, while the elders and those who actively seek Him will remain unharmed [מלבי״ם].
Conversely, another perspective views this thirst as entirely spiritual. The craving is not for water, but for the word of God and the guidance of prophecy, which will be completely cut off. The focus on the youth reveals a profound shift: even young people, who typically immerse themselves in worldly pleasures, will reach a point of intense yearning for God's voice [רד״ק, אברבנאל]. Overwhelmed by sorrow because God has turned away and no longer answers them, the young women will weep until their beauty is entirely ruined [אבן עזרא].
On a deeper, allegorical level, this imagery represents the entire nation. The beautiful young women symbolize the congregation of Israel, specifically the kingdoms of Israel and Judah. The young men represent all the tribes of Israel combined. Together, they will collapse in their exile, consumed by a desperate longing for the divine prophecy they have lost [אברבנאל].