The last two times we traveled long-distance by Amtrak, the snack bar ran out of cheeseburger, pizza, deli sandwich and hot pocket items, as the train progressed, and was resupplied only once in 2200 miles. Coach passengers were out of luck when asking to eat in the dining car. So, if you intend to travel by coach and the train will be on its second day out from its originating terminal, I'd suggest that you take something to sustain your hunger if the snack bar runs out of food items.
Also, on this topic, the snack bar now has one employee instead of two, and no matter how many passengers are waiting in line, when it comes time for the employee's break, everything stops.
One last thing about coach travel: Some of the passengers try to take two seats, and have other social behavior impediments. In this matter, it is a spin of the wheel of fortune.
