Preheat the oven
Set your oven to 375°F (190°C).
Lightly grease a small baking dish or line it with parchment paper.
Prepare the glaze
In a medium bowl, whisk together:
brown sugar
ketchup
Dijon mustard
soy sauce
apple cider vinegar
garlic powder
black pepper
Mix until the sugar begins to dissolve and the sauce looks smooth.
Combine sausage and sauce
Add the sliced kielbasa to the bowl and toss well so each piece is coated in the sweet glaze.
Arrange in baking dish
Spread the coated sausage pieces in a single layer in the prepared dish.
Pour any remaining sauce over the top.
Bake
Bake for 20–25 minutes, stirring once halfway through.
The sauce should become thick, sticky, and caramelized around the sausage.
Serve
Let the bites cool for 5 minutes, then transfer to a serving plate.
Insert toothpicks for easy grabbing and sprinkle with parsley if desired.