Fake ? Panel
From the Super Mario Wiki
Fake ? Panels, also known as Fake Question Panels, or ⸮ Panels, are items that appear in Mario Hoops 3-on-3. They are functionally similar to the Mario Kart series' Fake Item Boxes, which are also red, except the question mark in Fake Item Boxes is upside down rather than backwards. In the game they may be obtained from a ? Panel, after which they may be thrown onto any part of the stage at will. Once thrown, they will appear to be normal ? Panels but with a horizontally flipped ? mark. Any player that touches them will be flipped over and lose any coins they may have. When the Fake ? Panel is in a player's hand, it appears to be a red ? Block.