In a small bowl, whisk together coconut aminos, rice vinegar, minced ginger, and minced garlic.
In a separate tiny bowl, mix arrowroot powder with water to create a smooth slurry.
Season the cubed chicken breast with sea salt and black pepper.
Heat toasted sesame oil in a large skillet over medium-high heat.
Add chicken to the skillet and sear until golden brown and cooked through, about 5-6 minutes.
Add the bell peppers and red onion to the skillet, sautéing for 3-4 minutes until crisp-tender.
Stir in the pineapple chunks and the prepared sauce, then pour in the arrowroot slurry.
Simmer for 1-2 minutes until the sauce thickens into a glossy glaze that coats the chicken.
Meanwhile, lightly steam the cauliflower rice in a separate pan or microwave until tender.
Serve the sweet and sour chicken immediately over the warm cauliflower rice.