Place brown rice and water in the instant pot, close the lid and seal.
Cook the rice for 17 minutes on high pressure, followed by a quick pressure release.
Place the meatballs in the slow cooker.
Add in garlic, onions and carrots.
In a small bowl, add water to the pineapple juice to make 1½ cups.
Stir in the vinegar, brown sugar, soy sauce and cornstarch.
Pour over meatball mixture.
Cook on low for 7-8 hours or on high for 5-6 hours.
During the last 30 minutes of cooking, stir in the pineapple tidbits.
In the sauce is too runny at this point, vent the lid for the last 30 minutes to let it thicken up a bit.