Alternately thread ham, pineapple, sweet pepper, and tomatoes onto skewers (if using wooden skewers, soak for 30 minutes before grilling).
For a charcoal grill, place kabobs on the rack of an uncovered grill directly over medium coals for 3 to 5 minutes until heated through and browned, turning once. (For a gas grill, preheat grill. Reduce heat to medium. Add kabobs to grill rack. Cover and grill as above).
If desired, serve with sweet-and-sour sauce or your favorite sauce.