The hazard class of a two-liter bottle of material is Flammable Liquid. If the description also says Poison Inhalation Hazard you should:
If the words INHALATION HAZARD appear on the shipping paper or package, the rules require display of the POISON INHALATION HAZARD or POISON GAS placards, as appropriate. These placards must be used in addition to other placards, which may be required by the product’s hazard class. Always display the hazard class and POISON INHALATION HAZARD placards, even for small amounts.