I've got an upcoming trip on the EB. There will be three of us, all going by sleeper (each with our own room). Even with the diner available, I suspect we'll want to do some late night hanging out and snacking, so here's what we have planned:
A softsided cooler with ice will be stashed in one of the rooms with bottled water, soft drinks, and probably a bottle of port for before bed.
For snacks, we'll have dried fruit and nuts (pistachios and cashews were the Costco winner). Fresh baked cookies. And the best part, I think, will be supplies to make at least a couple of charcuterie boards (some meats, a variety of cheese, mustard, and hopefully some cold smoked salmon).
Packing list also includes hand wipes and clorox wipes to make things easier, as well as decent quality but disposable plastic plates, plastic cups, zip locs, and some trashbags for cleanup.