As I recall, Sano hit a long home run and, shall I say, over-celebrated. While that might be standard behavior in the Dominican here in the US that could lead to a fast ball in the ribs. (Many of us will remember the long discussion we had about this issue during the last year.) So Smith sat him down to reinforce that the home run itself is demonstrative enough and that there's no need to rub it in the opposing team's collective face. I'll edit this to add that I would guess that the suspension was also to let other teams know that the Twins organization was handling the issue so that other teams didn't need to add their own input in the form of the aforementioned fast ball in the ribs.