Melt the vegan margarine in a medium-sized saucepan over low heat.
Add the frozen corn, plant-based milk, sugar, salt, and pepper. Increase heat to medium and bring the mixture to a boil, stirring constantly.
Reduce the heat to low and let it simmer for 5 minutes, stirring occasionally.
Push the corn to the sides of the pan to create a pool of liquid in the center.
Sprinkle the cornstarch into the liquid and whisk constantly until it thickens and no lumps remain.
Stir the thickened sauce into the corn until everything is well combined.
Serve immediately.
Add a pinch of nutmeg or smoked paprika along with the salt and pepper for a warm, smoky depth of flavor.