In a bowl, combine soy sauce, sesame oil, honey, minced garlic, rice vinegar, and ground ginger to prepare the marinade for the steak.
Place the sirloin steak in the marinade, ensuring it is evenly coated. Let it marinate for at least 15 minutes, or up to 2 hours in the refrigerator for enhanced flavor.
While the steak is marinating, cook the rice according to package instructions if not already prepared.
Heat a skillet or grill pan over medium-high heat. Remove the steak from the marinade and cook for about 3-5 minutes on each side, or until it reaches your desired doneness. Remove it from the skillet and let it rest for a few minutes before slicing.
In the same skillet, add the sliced bell peppers and shredded carrots. Sauté for 2-3 minutes until they are slightly tender, then add the baby spinach and cook just until wilted.
To assemble the bowls, place cooked rice at the bottom of each bowl. Top with the sliced steak, sautéed vegetables, and drizzle with any remaining marinade if desired.
Garnish with sesame seeds and chopped green onions if using.