In a microwave-safe measuring cup, melt the apple juice concentrate. add the garlic, vinegar, hot sauce, pepper, salt, mustard powder and pepper flakes and stir together.
In a separate bowl, combine the flour with enough water to create a thickish, smooth paste. stir this into the apple juice mixture and whisk until no lumps remain.
Spray wok or pan with cooking oil and heat to medium-high. If using frozen veggies, add those first to let them thaw, then once they aren't frozen add the sauce and meat together. If using fresh, you can add it all at once. Cook until meat is tender, stirring occasionally. Add salt to taste.