Prepare the ingredients by chopping the garlic cloves into thin slices and the steak into bite-sized cubes. Set aside.(Optional) Rinse the sliced garlic to wash off the sticky bits on their surface then pat to dry. This helps remove the bitter taste of garlic. Marinate the steak bites with sugar, cornstarch, salt, black pepper, soy sauce, sesame oil, and water for 10-15 minutes.
Meanwhile, prepare the homemade teriyaki sauce by mixing together soy sauce, mirin, rice wine, and sugar.
Prepare the fried garlic. In a wok, add in about 1 tbsp oil and sliced garlic. Stir-fry over low heat until golden-brown crisp. Be patient with this step to prevent burning the garlic slices. As the oil becomes bubbly, increase the heat, and stir-fry quickly to achieve a crispy, crunchy texture. Set aside.
Using the same wok, heat another 1-2 tbsp oil then add in the marinated steak bites. Pan-sear both sides for 2 minutes maximum, then add in half of the fried garlic.
Add in teriyaki sauce, increase the heat, and stir-fry for another 1-2 minutes.
Transfer the garlic teriyaki steak bites to a serving plate and garnish with the remaining fried garlic.