In a large bowl, combine the beef sirloin strips with soy sauce and sesame oil. Marinate for 15-20 minutes.
Heat up some cooking spray or neutral oil in a wok over high heat. SautΓ© garlic until fragrant (about 30 seconds). Add the marinated beef strips and stir fry, breaking into smaller pieces for about two minutes per side to ensure they are fully browned but still pink inside.
Push the meat aside as you add your vegetables in. Stir-fry them until just tender. Return the cooked beef back into wok with veggies and stir everything together over high heat for another minute or so to combine flavors fully, adding salt if needed after tasting.
Grate fresh ginger root directly onto your dish right before serving.