Place the 4 boneless skinless chicken breasts in the bottom of the slow cooker in an even layer.
In a mixing bowl, combine 2 cups barbecue sauce, 1/4 cup light soy sauce, 2 tablespoons lime juice, 1 teaspoon ground ginger, 1 jalapeño, and 3 minced garlic cloves; stir until blended.
Pour the sauce mixture over the chicken so it is evenly coated.
Add the sliced red onion and the drained 20 ounces of canned pineapple chunks on top of the chicken.
Cover and cook on low for 5 to 6 hours or on high for 2 to 3 hours, until the chicken is cooked through and tender.
Remove the chicken to a cutting board, shred with two forks, then return the shredded chicken to the slow cooker and stir to combine.
Cook on low for an additional 15 minutes to let the flavors meld, then serve.
