I came across this post about Suggestion to "sleep" and wanted to know if there was any official ruling for what would happen if you Command someone to "sleep". There seem to be people that think it makes the target fall asleep but from my understanding of it the target would just lie down for 6 seconds, try their hardest to fall asleep, and that's it. Since it takes the average person 7 minutes to fall asleep they'd still be wide awake after you use the Command spell on them. Correct?
Twitter user: if I use suggestions to tell someone to “go to sleep” do I have an 8 hour sleep spell?
Crawford: The suggestion spell allows you to compel someone to pursue a course of activity. You could, for example, tell them to go to sleep. That doesn't knock them out; it causes them to try to go to sleep naturally. It isn't magical slumber.
Another user: Also, there's no guarantee they can actually sleep. E.g. telling someone to go to sleep in the middle of a battle should fail automatically.
Crawford: Given how hard it often is for me to go to sleep, casting suggestion on me and telling me to go to sleep would usually result in nothing at all!
For the Command spell, I imagine a "Sleep" command would be functionally equivalent to "Grovel", in that the creature would become prone and end its turn. However, this would only last for that one turn. Command doesn't cause magical slumber. The creature would try to fall asleep for that one turn, but nothing would cause it to sleep immediately. However, it's ultimately up to the DM, since the Command spell description says the following:
Some typical commands and their effects follow. You might issue a command other than one described here. If you do so, the DM determines how the target behaves. If the target can't follow your command, the spell ends.