U can apply a SiO2 or TiO2 layer on the glass via CVD or sol-gel method and then apply a hydrophobic material on it like 2%trimetiletoxicilane and 5%ethanol and deionazed water. but if the transparency of your glass isnt very important u can use my microwave method to synthesis ZnO nano structures and then combine this nano powder with solution that mentioned above. and then spray this composition on your glass