Evan Fournier's decision to go all David Beckham after losing to the Miami Heat just set him back a huge wad of dough -- the Detroit Pistons player was fined $25k for the move.
The moment went down shortly after the home team lost in devastating fashion ... with Bam Adebayo chucking up a game-winning three-point shot at the buzzer to secure the 104-101 win.
As the victors celebrated at center court, Fournier -- who had 18 points in the losing effort -- was in a much worse mood .