Mix ground ham, ground pork, eggs, milk, crackers, salt, and black pepper together in a bowl; form into a loaf. Transfer loaf to a loaf pan.
Mix brown sugar, cider vinegar, and dry mustard together; pour over the loaf.
Bake in preheated oven for 1 hour. Spread pineapple atop the loaf; continue baking until no longer pink in the center, about 45 minutes more. An instant-read thermometer inserted into the center should read at least 160 degrees F (70 degrees C).
