A fiber optic sensor coated with a thin film of zinc oxide nanorods has been developed to detect methanol in adulterated tequila. Zinc oxide was synthesized by ultrasonic method and was used as vapor sensing media. The measured intensities of transmitted light in the optical sensor were analyzed at different concentrations of methanol in tequila. The sensor presented good response to tequila-methanol mixtures and the observed differences in response and recovery times allowed and easy and economic detection of methanol in commercial tequila. The developed sensor is a simple and economic device to detect methanol in commercial tequilas or another beverage. Moreover, it can be used as a quality control technique in laboratories to distinguish the adulteration and/or contamination degree with methanol.