Buses and undergrounds don't allow consumables, but regional and long-distance trains do without any constraints. Long-distance trains have a dining car, but you're also free to take the snack items from the menu to your seat. In first class, they even serve you directly at your place. It's hardly a problem, apart from the occasional McBeetus-stank because someone wasn't able to eat before boarding, but people spilling stuff is seldom - except for drunk fucks or obeasts without motor skills.