Plastic Bottle Cap for Lego Pneumatics

I use it with a sparkling ice bottle, but it might work with other bottles.

(Assembly)

Drill a hole in the cap a little bigger than half an inch.

Apply glue to the base of the screw piece.

Push the screw piece through the cap so the glue is between the cap and the base of the screw, and the top of the screw is sticking out the top of the cap.

Screw the nut on tight to the screw but be careful with the nubs because they break when force it applied.