Set the electric smoker or pellet grill to 225 degrees Fahrenheit. Close the grates that allow the open fire or heat element to be exposed so that the tenderloin does not cook too quickly.

Brush the pork tenderloin with teriyaki sauce and sprinkle with toasted sesame seeds, if desired. (Toast sesame seeds in a pan over the stove for about 5-6 minutes, stirring constantly until lightly browned.)

Spray the smoker grates with nonstick cooking spray so that the meat does not stick and tear apart. Place the pork tenderloin on the grates and close the lid. Allow to cook for approximately 1-1.5 hours, until the pork has reached at least 145 degrees Fahrenheit.
Note: I like to use wireless internal thermometer probes anytime I cook on the smoker. The link is below to the one I bought from Amazon.

If you like more caramelization, open the grates so that the heat element/fire is exposed to the meat and brush the pork with more teriyaki sauce. Let it cook for the last 10-20 minutes with the grates open.