Does Allah answer a supplication against oneself or another, uttered forgetfully or unintentionally due to drowsiness and fatigue? And do the angels say "Ameen" to it?

The Prophet, peace and blessings be upon him, forbade praying while drowsy and commanded one to rest and sleep until the drowsiness departs, so that the worshipper does not inadvertently curse himself and so that he knows what he is reciting.

It was said that the reason for the prohibition was the fear that the hour of answered prayers might coincide with the worshipper supplicating against himself. It was also said that the reason is the fear of confusion in what the worshipper recites and supplicates, and the matter of recitation is more severe because it is obligatory, and the corruption in altering the Qur’an is great.

As for the question of how a servant can be held accountable for something he did not intend to utter, the answer is that whoever exposes himself to falling into that after the prohibition is transgressing. Also, the purpose of prayer is to perform it as commanded and to achieve supplication. If the purpose is missed due to not knowing what was recited, and due to the non-fulfillment of his supplication, then he is forbidden from burdening himself with something that has no benefit.