t3hlazy1

You're the one posting the "$100,000 watch on sale for $75,000" threads.

Lol, I didn't realize you meant sunburn at first, and was very confused.

https://giphy.com/gifs/thedannychang-pizza-the-office-1msy0o1Ma3bsLYBZUA

Double-sided cards. Notice the orientation of his hand before and after the switch. He is probably twisting the glass really fast then stopping, allowing the cards to keep moving and do a 180 degree.
So the trick goes:
The cards in the first glass are double sided, so that they appear to be in order when shown to the audience, but the opposite side is pre-prepared. One of the cards is not double-sided, this allows him to flip it around and make the audience believe the cards aren't double-sided.
He hands regular cards to an audience member, retrieves these, and switches them for prepared cards. It appears he guides the second audience member to choose the middle card to be flipped, to match the first deck. If the second audience member is not cooperative, maybe he has a backup plan.
Then, all he has to do is flip the cards in the glass around, which I explained in the beginning.

This is all just guessing, as I know nothing about magic.

Take one for the other team, as it were.