In a large bowl, combine beef with bread crumbs, egg, salt, coriander, and horseradish. Mix thoroughly. Shape into 32 small balls. Roll each ball in cornstarch. Heat oil in wok to 375 degrees F. Fry meatballs a few at a time until browned. Remove and set aside. Drain oil from wok.
Mix sugar, vinegar, soy sauce, sherry, tomato sauce, and cornstarch to make sweet and sour sauce.
Heat 1 tablespoon of oil in wok. Add garlic and fry until browned. Remove garlic and discard. Add onion and stir-fry for 30 seconds. Reduce heat. Add meatballs, water chestnuts, and pineapple chunks. Pour in sauce and stir until heated.
Serve over rice.