For savory dishes like this flank steak, you can replace 1 cup of molasses with the same amount of honey, dark corn syrup, or maple syrup, but you'll forgo the big, robust flavor of molasses.
For baked goods like spiced cookies or cake, you can replace 1 cup of molasses with a mixture of 3/4 cup sugar, 1 1/4 teaspoons cream of tartar, and 1/4 cup of hot water or other liquid that is in the recipe. If there are spices in the recipe, increase them just a little to compensate for the loss of the molasses flavor.
One caution: But don't use blackstrap molasses if your recipe calls for light molasses: blackstrap has an even more intense flavor that may be overpowering.
View Recipe: Molasses Cookies