SOAK 30 to 40 small skewers in water for at least 30 minutes. Preheat grill to medium-high heat and brush grates with oil.
COMBINE ketchup, brown sugar, soy sauce, pineapple juice, sesame oil, garlic, ginger and vinegar in a small bowl. Set aside for brushing skewers.
THREAD 2 sausages widthwise onto skewers followed by one pineapple cube. Repeat with remaining sausage and pineapple.
GRILL skewers, occasionally brushing with ketchup mixture, until sausages and pineapple are lightly charred, about 2 to 3 minutes per side.
SERVE skewers with remaining sauce and enjoy.