Challenge — can you get these cups unstuck?

Here's something I wrote about in the latest issue of my newsletter, The Magnet:

A few days ago my daughter put a small cup in a large cup and they somehow got locked together. I can't pull them apart (watch video). Do you have any ideas on how to take them apart without breaking them? The first person to suggest a successful solution gets a free one-year subscription to The Magnet, which they can use for themselves or as a gift subscription.