Spin Boost Pillar
From the Super Mario Wiki
Spin Boost Pillars are objects found in most races of Mario Kart 8 and Mario Kart 8 Deluxe. They are only found in anti-gravity areas and their appearance usually changes depending on the track they are found on. When a racer drives into one, they will spin and gain a short speed boost, similar to what happens when two racers bump into each other in an anti-gravity segment. Certain objects can also act as Spin Boost Pillars, such as the wheels of the submarines during the loop in Water Park. In Hyrule Circuit, driving into the three Spin Boost Pillars in the castle within a short period of time will create a Dash Panel over the platform in the next room.