Is it permissible to use a character in a story who drinks alcohol for the purpose of portraying them as unconscious, given that the act of drinking is secondary and without commentary?

There is no harm in writing fictional novels and stories if their aim is reformative and guiding towards goodness and noble human values, and provided that they do not include the mention of evil deeds except to show their bad consequences and to learn lessons from them, and not for glorification or endorsement. If they are meant to address an ailment that has afflicted people, then there is no objection to them, on condition that they are presented in a way that indicates they are not real, serving as parables to draw lessons, and not recounted as factual events, because that would be a lie. However, if they lead to sin and transgression, then they are forbidden.