Heat a small sauce pan over medium. Ad in 1 tbsp water, garlic powder, sweetener, and soy sauce. Stir and leave to simmer and come to boil over medium heat. Feel free to add more sweetener if you want it sweeter.
Meanwhile, mix together the corn starch and water in a small bowl until you have a slurry.
When the sauce has come to a boil, lower the heat to medium low and then stir-in the slurry. Give the sauce a good mix. It’ll slowly start to thicken. Turn off the heat. The sauce will continue to thicken as it cools. If you want a runnier sauce, feel free to add a bit more (around 1 tbsp more) water.You can also adjust the sauce depending on your desired taste.
Storage and making ahead: you can store this in the refrigerator until ready to use. It can thickened form some clumps when refrigeratred so you can simply reheat this quicklythe microwave and give it a good stir to dissolve any clumps from the starch.