1) Be the sort of jerk who would intercept a ball being tossed to a child fan.
2) Once the player (for the opposite team) who tried to be generous turns around, throw the ball and hit said player in the back.
This actually happened at Yankee Stadium yesterday. Alex Verdugo tossed a ball to a kid there as a Red Sox fan, and some idiot snagged it and hit Verdugo with it. That person was immediately ejected from the ballpark. Today said “fan” was in formed he was permanently persona non grata at all 30 major league venues. What a bone head. He’s lucky that Verdugo was not actually injured.
For what it’s worth, the Yankees won a 6-inning, rain shortened game, 3-1.