1) In large bowl, mix together beef, onion, crackers, black pepper, egg whites and half the can of tomato sauce. (This works best if you use your hands to mix ingredients.)
2) Form the mixture into a loaf shape and place in deep baking pan or loaf pan.
3) In a separate bowl, put remaining 1/2 tomato sauce, vinegar, dry mustard, and brown sugar. Mix well and pour over meat loaf.
4) Drizzle the water around the edge of the meat loaf in the pan.
5) Cover loosely with foil and cook in 350 degree oven for 45 minutes, then uncover and cook an additional 15 minutes or until cooked through thoroughly.