Step 1

Turn on a multi-functional pressure cooker (such as an Instant Pot®) and select Saute function. Add oil and heat until hot. Add pork cubes, working in batches if necessary, and cook until browned on all sides, about 5 minutes. Return all the pork back to the pot and cancel Saute mode.

Step 2

Whisk together 3/4 cup water, ketchup, rice vinegar, pineapple juice, brown sugar, soy sauce, ginger, and garlic in a small bowl. Pour over pork and stir to combine.

Step 3

Close and lock the lid. Select high pressure according to manufacturer's instructions; set timer for 5 minutes. Allow 10 to 15 minutes for pressure to build.

Step 4

Release pressure using the natural-release method according to manufacturer's instructions, about 5 minutes. Release remaining pressure using the quick-release method. Unlock the lid and remove. Transfer pork to a plate using a slotted spoon. Cover with foil to keep warm.

Step 5

Select Saute mode and stir in onion, pineapple, and red and green bell peppers. Simmer until vegetables start to soften, 6 to 7 minutes.

Step 6

Whisk together cornstarch and remaining 1/2 cup water in a small bowl until smooth. Pour slurry into the pot. Cook, stirring constantly, until sauce has thickened to your preferred consistency, about 2 minutes. Return cooked pork back to the pot and heat until just warmed through. Garnish with sesame seeds.