It has about half the sweetness of white sugar (sucrose) and one-third the sweetness of honey.
The rice is cooked, fermented with enzymes to free up the starches, then strained and the liquid is simmered until thick. Some brands add some barley malt syrup.
The syrup is also sold in a powder form, that dissolves easily in water.
Using it in baked goods tends to make them hard or crisp.
Substitutes
For each part Brown Rice Syrup called for, substitute 1/2 part molasses or 3/4 part Barley Malt Syrup or 3/4 part honey or 3/4 part maple syrup.
You can swap Brown Rice Syrup into a recipe replacing white sugar: for each part white sugar called for, swap in 1 1/3 parts Brown Rice Syrup. For every 5 oz (150ml) of Brown Rice Syrup you swap in, reduce other liquid in the recipe by 2 tablespoons.
Nutrition
Brown Rice Syrup is about 45% maltose, 3% glucose, with the remainder being largely complex carbohydrates. It contains only trace amounts of minerals and vitamins.
It is absorbed slowly by the body.