Is there an achievement for getting the basketball in the hoop?

Other than a rightly-earned feeling of self-satisfaction, there are no achievements or game-related consequences to sinking a basketball, yet¹.

You can watch this player sink a ball at around the 20 second mark.

_{¹ The key word being yet. Blizzard have snuck in Easter egg achievements with content updates in the past, so don't put it past them to do it again.}

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:

With the most recent update to the game, sinking a basket now yields an air horn and some celebratory confetti:

Still no achievement, but at least it's acknowledged now :)