https://www.cnet.com/news/ant-man-and-the-wasp-post-credits-scenes-explained-avengers-infinity-war/

A huge Giant-Man-sized spoiler warning here! If you don't want to know what happens during the post-credits scenes in Ant-Man and the Wasp, then stop reading now. In addition, if you don't want a good bit of the plot of the actual movie spoiled then also stop reading now. We good? Good.  

The scene starts on a rooftop. Hank Pym (Michael Douglas), Janet Van Dyne (Michelle Pfeiffer), Hope Van Dyne (Evangeline Lilly) and Scott Lang (Paul Rudd) are all there. After the events of the movie, they've now successfully shrunk the quantum tunnel and have placed it in the back of a van.