There are no achievements for getting the basketball into the hoop.
Gameplay-wise, however, is an entirely different manner. When the ball lands in the hoop, an airhorn sounds along with a shower of confetti in your ship.
But besides being able to be used for entertainment, basketballs can be used for even greater sources of entertainments by adding traps to them.
Not only can Symmetra's sentries be placed on a basketball, allowing you to knock it into the air, and hopefully get a few kills as it flies through the air,
Junkrat's Steel Trap and Concussion Mines can also be attached for some hilarious shenanigans: