If you have no molasses, no maple syrup, no honey, and no coconut sugar? You have discovered the Void of Desperation. In this case, use equal parts white sugar and any jam or fruit preserve that’s brownish (fig jam is a champ, strawberry jam is a liar). It won’t be brown sugar, but it will be a fun, fruity mutant version of your recipe.
Congratulations. You have now replaced brown sugar with the chaotic energy of a raccoon in a bakery. Go bake that dough, and remember: no one ever died from a slightly weird cookie. They just wrote a mean Yelp review, and you can always block those people.