Mix marinade: garlic, cornstarch, water, soy sauce, olive oil and wine and marinate the steak slices for 30 minutes.
Meanwhile make the sauce: stir together water, corn starch, soy molasses, wine.
Remove steak from marinade, discarding the marinade.
Heat 1 tsp olive oil in a large skillet over medium-high heat and cook half of beef at a time without stirring, 45 seconds or until browned; turn beef, and cook 45 seconds or until browned. Transfer to a warm plate.
Stir-fry the onion until tender, about 2 minutes.
Add sugar snap peas, carrots, ginger, and crushed red pepper; stir-fry 2 minutes.
Add beef and sauce mixture; stir-fry 1 minute or until slightly thickened.
Remove from heat.
Stir in watermelon.
Add black pepper, and red pepper to taste.
Serve immediately over brown rice.