Combine the 1 cup of water, soy sauce, sesame oil, sugar, ginger, and garlic/garlic powder in a saucepan over medium heat. Cook until sugar melts, about 5 minutes. Reserve 1/4 of it aside and let it cool.
Combine 2 tbsp of corn starch with ¼ cup of water and mix until lump free. Stir into the rest of teriyaki sauce in the pot and simmer for a few minutes or until sauce thickens.
Rinse, pat salmon dry and place into the cooled marinade without the cornstarch and set aside for 15 minutes.
After 15 minutes, discard the marinade liquid and spray the salmon with olive oil.
Preheat grill to 400°F and place the marinated salmon on the grill skin side down. Cover and grill for about 8 minutes. Open cover and flip, cook for another 5-8 minutes or until desired doneness.
Garnish with more teriyaki sauce, sesame seed and green onion. Serve immediately with rice and vegetables of choice.