I am finding out that trains in Ukraine can be very 'third world'. The toilets are unsanitary and cramped, I could smell second hand smoke through the air vents and they didn't have a restaurant car or meal services on an overnight train. At least on an Indian train, you will never be wanting for food or water.
We paid for a private'luxe' coupe but all there was to show for it were plastic plants (lots of them), formica coupe walls and depressing seat fabric. All night the train kept halting abruptly and then jerking forward. The only saving grace - Ukrainian trains run on time.