A bag includes a sealed hollow body and water-soluble powders contained in the body for removing an oil film on a windshield of a vehicle. The body is soft and permeable. Preferably, the body is water-absorbable. Preferably, the water-soluble powders are made of an inorganic material selected from a group consisting of magnesium oxide, calcium oxide, manganese oxide, copper oxide, calcium silicate, silicon dioxide, aluminum oxide, iron oxide, and mixtures thereof.