At one time Amtrak did provide free soda in the sleeping cars. That practice stopped about 4 or 5 years ago in part due to budget cuts at that time forced upon Amtrak by Congress. The secondary reason for their loss was hoarding of the soda by a few. And that few included both passengers and crew.Look I spent 26 hours up and down from DC. There is no reason why they can't have sodas etc... 24/7. I know the trains are old why not at least retro fit them with WiFi and dare I say a small flat TV screen in each sleeper? They do this on the airlines. Amtrak is offering a very slow service. They should at least equal airlines with comfort or at least try.
Yes, there were a few crew members who would not put out their entire stock of soda and instead take it home for their own use or to sell. And there were also passengers who would grab 4 or 5 sodas every time they passed by the beverage station and go home with 10, 15, 20 or more cans of soda.
So again, when ordered by Congress to cut food service losses, free sodas in the sleepers were an easy and to some extent a logical place to start.