An oral appliance for administering a stimulus, such as a substance, to the mouth of a user includes a flexible tube having an inlet portion, a first curved portion forming an ear loop connected to the inlet portion, a second curved portion forming a lip bend connected to the first curved portion, and an outlet portion extending from the second curved portion. Alternatively, a mouthpiece for delivering a substance to the mouth of a user includes a housing having an inlet portion, a riser portion extending upwardly from the inlet portion and a curved outlet portion. A flexible tube is coupled to the housing. A method of delivering a substance to a predetermined location in a user's mouth includes disposing a flexible tube between a row of teeth and an interior surface of a cheek. The flexible tube has an exit port positioned in a rear portion of the user's mouth. No portion of the flexible tube is disposed between the upper and lower teeth of the user such that the upper and lower teeth can be closed against each other. The method further includes dispensing a substance through the exit port.