If your no-bake cookies are too wet and thin, it's not too late to fix them! You can thicken it up by adding more peanut butter and/or oats. But do so a little at a time and stir well. The hot mixture will also thicken as it cools, so it should be a thick but pourable consistency when you start scooping. You can also return the mixture to a boil to thicken it, but I don't recommend doing so if you've already added the peanut butter and oats. If your cookies failed and are dry, sadly they can't be saved easily. But you can crumble the mixture for ice cream topping, milkshakes, or other desserts.