Add 2 cups of fresh or frozen blueberries to a sauce pan and heat over low-medium heat for 5-7 minutes, stirring occasionally.
Once the blueberries are nice and soft, use a fork or potato masher to squish them as much as possible to release the juice.
Then stir in 1/4 cup of sugar and allow the homemade blueberry syrup to simmer for around 5 minutes or until the liquid reduces slightly.
Either strain the blueberry syrup for a smoother consistency or use as is.
Notes
Frozen berries will need to be heated through for closer to 7 minutes. Add a lid to help the process along.
You can omit the sugar, especially if you're using wild blueberries, or add more if you like it sweeter.
For a thinner blueberry syrup, you can add water a tablespoon at a time until you've reached the desired consistency.
If you want your homemade blueberry syrup to be smooth, use a fine mesh strainer or a coffee strainer to remove any seeds or the outer layer of the blueberry.
Keep the syrup in an airtight container in the refrigerator for 3-5 days or freeze it.