Mix together the soy sauce, vinegar, sugar, water and cornstarch. Set aside.Prep your green beans by snipping off any ends that need it.In your large skillet (or wok if you have one), heat your oil on medium heat for about 30 seconds, add in your garlic and red pepper flakes and cook for 30 seconds, stirring constantly.Add in your green beans and cook until either crisp tender or more wilted, whichever is your preference. Depending on the size of your green beans 3-5 minutes. Quickly remove green beans with a slotted spoon.Pour in your soy sauce mixture. Allow the mixture to come to a boil (30-45 seconds). add back your green beans, coat with sauce and continue to cook for another minute.Serve & enjoy!