Rinse the brown rice under cold water. Cook according to package directions. Once tender, season with salt and black pepper and set aside.
In a small bowl, mix together the tomato, red onion, cilantro, lime juice, and salt to prepare the pico de gallo. Set aside to allow the flavors to meld.
In another bowl, mash the avocado until smooth, then stir in the lime juice, red onion, cilantro, and salt. Cover and refrigerate until ready to serve.
Pat the chicken dry and season evenly with chili powder, cumin, garlic powder, salt, and black pepper.
Heat the oil in a skillet over medium heat. Add the chicken and sauté, stirring occasionally, to an internal temperature of 165°F (74°C).
Using the same skillet, heat olive oil over medium heat. Add the bell pepper and onion and sauté until softened and onion is lightly caramelized.
Warm the flour tortillas in a dry skillet or microwave until soft and pliable.
Assemble the burritos by layering brown rice, chicken, sautéed peppers, onions, pico de gallo, and lettuce onto each tortilla. Fold in the sides and roll tightly.
Combine the sparkling water, lemon slices, and chia seeds. Stir well and let sit for 2–3 minutes to allow the chia seeds to hydrate.
Serve the burritos with tortilla chips, guacamole, and lemon chia sparkling water.