When Lily is pouring "tea" from the pot, it's clearly just water.
When Barney and Robin use the escape chute at the end of the episode, the entire wall and the attached security camera wobble showing that it is just a wooden backdrop.
Barney lowers a green screen on the balcony which those viewing his apartment see as being cityscapes from around the world. This is not how green screens work, and would require them to watch the scene through a monitor.