Most fire bombs are simply gasoline filled bottles with a fuel soaked rag in the mouth (the bottle's mouth, not yours). The original Molotov cocktail, and still about the best, was a mixture of one part gasoline and one part motor oil. The oil helps it to cling to what it splatters on. Some use one part roofing tar and one part gasoline. Fire bombs have been found which were made by pouring melted wax into gasoline.