I haven't made beef and noodles in a while but I have this beef stew seasoning packet and wanted to try that instead of beef broth or the beef cubes. Would this work? How much water would I need? I am just making a regular amount with one package of noodles and a can of shredded beef. 
So you have this seasoning mix, as per comments. Ingredients are, with my comments:  Corn Starch thickener Salt obvious Onion goes well with beef, found in most "beef noodles" recipes I glanced at Sugar a bit of it does wonders to beef taste, in my opinion Spices (Including Paprika, Black Pepper, Thyme) that's what I add to my beef, too Tomato questionable, but I see how it can be good Hydrolyzed Corn Gluten thickener, mouthfeel Soy Protein and Wheat Gluten as above Caramel Color obvious Citric Acid Xanthan Gum (Thickener).  So will this make a beef noodles as a stand in replacement? I think not. It doesn't have any beef taste on its own. And if you will try to boil canned beef with it long enough for taste to mix in, you will overcook your beef. Consider either using these ingredients separately, as they were probably meant to be used, or treating it as an experiment. Personally, I like beef overcooked in sauce to the point there are no longer visible beef pieces, just one smooth thick sauce. But that's quite far from what you would usually call beef noodles. 