A spill-proof motor oil bottle has a neck and a fluid reservoir with flexible sides. The neck has a first narrow portion, a relatively wider chamber adjacent to the first narrow portion, and a second narrow portion adjacent to the chamber. The bottle has a fluid flow path defined from the fluid reservoir through the first narrow portion, the chamber and the second narrow portion. The fluid flow path interconnects the two narrow portions and the chamber. A flexible plug, which is usually made of a compressible closed cell material, is compressed by and lodged within the first narrow portion to block the fluid flow path. The plug is adapted to dislodge from the first narrow portion into the chamber to open the fluid flow path when motor oil in the fluid reservoir displaces toward the neck of the bottle in response to a user squeezing the sides of the fluid reservoir. A method of dispensing a liquid with the bottle includes turning the container upside down, inserting at least a portion of the neck of the bottle into an engine opening into which the motor oil is to flow, and then squeezing the flexible portion of the fluid reservoir to dislodge the plug from the first narrow portion of the neck and into the chamber, thereby opening the fluid flow path so that oil flows out of the bottle and into the motor.