Preheat the oven to 350 degrees F. Line two 12-cup muffin tins with paper baking cups and spray the papers with nonstick cooking spray.
Mix together the flour, brown sugar, salt and allspice in a large bowl. Cut in the butter until the mixture is crumbly. Set aside 1/2 cup for the topping. Stir the water, molasses, oil, baking soda and vanilla into the remaining flour mixture.
Fill the paper-lined muffin cups two-thirds of the way full with the batter. Sprinkle with the reserved crumb mixture. Bake until a toothpick inserted near the center comes out clean, 20 to 25 minutes. Cool for 10 minutes before removing from the pans and transferring to wire racks to cool.