Read notes for ingredient substitutions.

Combine ground beef, grated Spam, water, cornstarch, and grated onion in a bowl. Mix well with gloved hands.

Shape the meat mixture into 6 patties, slightly larger than the buns.

Season patties with salt and white pepper and refrigerate.

Whisk pineapple juice, sake, teriyaki sauce, brown sugar, ketchup, cornstarch, lemon juice, sriracha, garlic powder, ginger, and onion flakes in a bowl.

Heat sauce in a non-stick skillet until thickened, stirring constantly. Reduce heat and keep warm.

Butter and attach cut sides of Hawaiian rolls to keep fresh.

Cook bacon until crisp (optional). Slice vegetables and pineapple.

Immerse onion slices in the sauce until softened.

Preheat grill to medium-high. Grill patties and pineapple slices until grill marks appear and cooked to your liking.

Toast buttered buns on the grill until golden.

Coat grilled pineapple in the heated sauce.

Spoon sauce on top bun portions.

Coat grilled patties in the sauce. Place cheese slices over patties and melt.

Transfer patties to bottom bun halves. Stir green chilies into the remaining sauce.

Assemble burgers with bacon (optional), pineapple, onion, and lettuce.

Spoon sauce over grilled side of top bun. Place top buns over burgers.

Serve immediately.