Coach Passengers on the Auto Train have dining car meals included.
Coach Passengers on all Long Distance trains except for Auto Train, pay for meals in the dining car, and all snacks.
Business Class Passenger on the Auto Train receive 2 bottles of water, meals in the "Sleeper Class" dining car, and a comfort kit.
Business Class Passengers on the Coast Starlight receive 2 bottles of water, a coupon for a certain amount ($6.50?) off a purchase in the dining car or the lounge car.
Business Class Passengers on the Crescent and Cardinal receive a non-alcohol beverage only.
Sleeping Car Passengers on all trains except the Silver Star (as noted above) receive meals in the dining car for free which includes side salads at lunch and dinner, desserts at lunch and dinner, non-alcoholic beverages at all meals, and "extra" cost items such as a side of bacon at breakfast, bacon or cheese on a burger at lunch, etc.
Sleeping Car Passengers also get complimentary coffee and juice in the morning, and at least 2 bottles of water per trip. (Some Sleeper attendants offer bottled water throughout the trip, some refuse to give you more than 2.)
That should cover it for the Long Distance trips.