In a small bowl, whisk together the pineapple juice, tamari, rice vinegar, honey, and arrowroot powder until the starch is fully dissolved.
Season the diced chicken breast evenly with the sea salt and black pepper.
Heat the avocado oil in a large skillet or wok over medium-high heat until it begins to shimmer.
Add the chicken to the skillet and sear for 5-6 minutes, stirring occasionally, until the pieces are golden brown and cooked through.
Remove the chicken from the pan and set aside on a plate; add the sliced bell peppers and snap peas to the same skillet.
Sauté the vegetables for 3-4 minutes until they are tender-crisp and maintain their bright color.
Return the cooked chicken to the skillet and pour the prepared sauce mixture over the ingredients.
Stir constantly for 1-2 minutes as the sauce bubbles and thickens into a glossy, translucent glaze that coats everything.
Serve the stir-fry immediately over the warm cooked brown rice for a complete, balanced meal.