It occurs to me that the first question is whether or not such a “crash” really exists. Most “common knowledge” seems to be wrong about the effects of drugs (or even sugar - there’s no such thing as a sugar rush).
If it does, let’s say I have to get up considerably earlier than I’m used to, and therefore need to go to sleep sooner than my body is likely to accept. In these situations, I often find going to bed too early just leaves me lying awake for half the night, so I need to find a balance between being able to fall asleep and being able to spend a reasonable amount of time remaining asleep. In such an instance, would/could caffeine help me sleep if I timed the “crash” for shortly before my planned bedtime?
Caffeine has a half life of about 3.5 hours. If you drink coffee within 8-10 hours of going to bed, it will still be in your system when you sleep, and will lower the quality of your sleep. The drowsiness you may feel from a caffeine “crash” is either exhaustion or dehydration, both of which may disrupt your sleep.
I would recommend avoiding caffeine in the afternoon if you need to sleep early, and possibly drink camomile tea instead to help you fall asleep.
The OP is proposing to avoid the problem of sleeping at the wrong time so as to be able to sleep normally ,ie starting at the right time and for the proper length of time. That makes perfect sense… avoid the effect that is like “jet lag”…
Its not clear how caffeine interferes with sleep …but its probably in high doses that it happens, a simple “stay awake” dose of caffeine for a non-addict is probably not going to be a problem, is it ?
Its also possible to have a short nap, say a half hour or hour, in the afternoon, in order to recharge and yet still feel sleepy at the normal time. Perhaps have the coffee after the nap, so that you can wake up from the nap and be effective…