Can I Substitute Brown Sugar for White Sugar
If you’re making something dense and forgiving—think oatmeal cookies, gingerbread, or a hearty banana bread—go ahead and swap one-for-one. You won’t notice a problem. In fact, you might get a fluffier crumb because of that extra moisture.
Your cookies might be a tad chewier, which is usually a win. Nobody ever complained about a chewy cookie. Unless it’s supposed to be a crisp biscotti, but let’s be honest, you’re not making those on a whim.
The annoying science part (explained like you’re five)
White sugar is a bit of a neat freak. It stays dry and helps things spread out in the oven. Brown sugar is a messy hug. It holds onto water and makes baked goods softer and a little more dense with feelings.
If you swap brown for white in something like a delicate angel food cake, you’ll get a sad, flattened bird. Angel food cake needs that pure, dry structure. Don’t do it. You’ll just end up with a pancake that feels bad about itself.
Top 10 Brown Sugar Substitutes - The Nutrition Insider