Yep. Many people sleep in coach.
In fact the vast majority of Amtrak long distance train riders travel in coach.
Some sleep well, some have trouble sleeping, and some fall in between the 2 extremes.
I fall in between, but sleep well enough that I'm not overly tired the next day.
This last Monday I traveled from Ottumwa, Iowa to Denver in coach.
There weren't a lot of coach passengers and everyone pretty much had 2 seats to themselves.
They like overnight coach passengers going to the same destination to sit in the same area of a coach car to make it easier to ensure everyone wakes up in time to get off at their stop.
Someone mentioned earlier about the space behind the seats at the end of the coach being used as a sleeping space.
Sometimes the
Train Attendant - Coach puts a trash container or 2 there.
Some coach passengers sleep in the Sightseer Lounge (SSL) car.
Some lay across one of the 6 'couches'
in the middle of the SSL car that have a kink in them that functions like a triangular table between 2 of 3 seats. (seat, seat, table forms kink, seat).
Some sleep on the floor between the seats and the windows/sides of the car.
Many that sleep on the floor, or on one of the 'couches', sleep in a sleeping bag.
Passengers that sleep in the SSL are sometimes referred to as 'lounge lizards', and the conductor rousts all the lounge lizards just before sunrise so early rising passengers (coach and sleeper) can sit and watch the sunrise from the SSL car.