Just plug into a hotspot from xingwang's blog

Lastly, the Collector's Edition also gives players access to the Switch-exclusive Battle-Cars.For those curious, the game features support for the Switch's different play modes, and wireless local multiplayer is also offered. The modes and features playable in other versions of the game are also retained for the Switch edition.

Developers had also mentioned previously that they are still planning to Rocket League Items  release new features and improvements for the game in 2018.More news about "Rocket League" should be made available in the near future.

Imagine playing Rocket League on the go. Just plug into a hotspot, sit back, play a few matches, then head back home and sink in another couple hours. Sound appealing? That’s the premise behind Rocket League on Nintendo Switch, and it’s an incredible portable premiere for the vehicle-based soccer title.