We have examined a nondestructive and contactless screening method for water and inflammable liquids stored in common beverage plastic bottles by the terahertz time-domain spectroscopy. No THz transmission has been observed between 10 and 60 cm-1 for 45-mm-thick water in plastic bottles. Part of the THz wave, on the other hand, has been transmitted through the commercially available inflammable liquids in the same bottles. The differences in the absorption intensities and the refractive indices in the THz region, which reflect the ingredients of organic compounds, allow us to distinguish these inflammable liquids. We confirm that the screening method based on the THz transmission can be applied to classifying the commercially available inflammable liquids stored in plastic bottles and to distinguishing these inflammable liquids from water as well.