sumos gourge themselves on some kind of milk too- saw a special on their training awhile back-
Famous Mean Joe Green Coke commercial;
https://www.youtube.com/watch?v=xffOCZYX6F8
Japanese version of it with a sumo wrestler( starts @ 6:42);
https://www.youtube.com/watch?v=HrQONaLqbxc
They drink something like a case of beer a day too. The beer and rice really are what packs on the pounds. It looks like the soup is the protein and veg part of the diet, and probably not the biggest part of the weight gain.