In a shallow glass or ceramic dish, mix soy sauce, garlic, and oil. Add beef and coat it with the mixture. Cover and refrigerate for 1 hour to marinate.
Mix the lime juice, fish sauce, and sugar together in a bowl.
Preheat a barbecue flat plate or large frying pan over medium-high heat. Drain the beef from the marinade and cook for 3-4 minutes on each side for a medium cook or until it reaches your desired doneness. Transfer the beef to a plate, cover it with foil, and let it rest for 2 minutes before thinly slicing.
Cook the snow peas in boiling water for 1 minute until they are tender crisp. Drain them afterwards.
In a large bowl, mix together the dressing, beef, snow peas, spinach, mint, cucumber, onion, and tomato. Season with pepper and add the noodles on top.