To make the sweet & sour sauce: Combine all sauce ingredients, except for the cornstarch, in a small saucepan and bring to a simmer. Stir in the cornstarch mixture and stir until thickened. Set aside until ready to use.
To make the meatballs, thoroughly combine all the meatball ingredients in a large mixing bowl and form the mixture into 1-inch meatballs. Yields about 24 meatballs.
Alternately thread six bamboo or metal skewers with the meatballs (4 on each skewer), pineapple and vegetables. Brush with about half of the sweet & sour sauce.
Heat the grill to medium-high heat and brush the grill grates with some oil. Grill the kabobs about 5-6 minutes on each side or until lightly seared and the meatballs are cooked through.
Brush the kabobs with remaining sweet and sour sauce and serve immediately.
These kabobs are a perfect time-saving, make-ahead meal. You can make the sauce and thread the skewers well in advance and then keep both covered and refrigerated until ready to use.