Line a large Dutch oven with parchment paper. Prepare a chimney of coals for Dutch oven cooking. You'll need 30 coals to start. The coals are ready when they turn white all over.
Remove the biscuits from the can and cut each one into four pieces.
Combine the granulated sugar and cinnamon in a resealable bag. Working with a few pieces at a time, drop the biscuits into the bag, close and shake to coat each piece. Arrange the pieces in a single layer in the Dutch oven.
Scatter the raisins over the top of the biscuit dough, if using.
In a small saucepan over low heat, combine the butter and brown sugar. Let the butter melt, stirring occasionally, and then mix well to dissolve the sugar.
Pour the brown sugar and butter evenly over the biscuits. I find it easiest to spoon the glaze out of the saucepan and drizzle it over the biscuits. This allows for more even coverage.
Cover the Dutch oven with its lid and cook with 10 coals below and 20 on the lid, replacing the coals as needed, until the bread is puffed and set, 35 to 45 minutes. The internal temperature should be around 200°F (93°C).
Remove from the fire pit and serve warm.