If it was gum or candy, and michael had no idea he was receiving something, his first instinct would be to open his hand and look at it. The very fact he didn't even look at his hand tells me he knew he was receiving something. He never once opened his hand, tried to keep it out of sight.
In my opinion it looks like something fitting the description of a narrow rectangular thumb drive is being shifted into place as michael adjusts it in his hand and keeps it hidden from cameras.
Why would you hide gum or candy being given to you from an ex president. If it was gum or candy a normal person might of opened it up and ate it there on the spot, especially if its a piece of gum or mint.