Squeaky Clean Sprint

Squeaky Clean Sprint is a course featured in Wave 5 of the Booster Course Pass for Mario Kart 8 Deluxe. The course is set in a giant bathroom, similarly to how 's Mario Kart 8 appearance is set in a giant bedroom. The course takes racers through various departments within the bathroom, such as counters, shelves, bathtubs, and drains. According to internal data, this course was created as a new course for Mario Kart Tour, despite being revealed for Mario Kart 8 Deluxe first, similar to Sky-High Sundae and Yoshi's Island.

Throughout the course are various items commonly found in a bathroom. The starting banner is held up by two cups, each containing scissors, toothpaste, a toothbrush and a hairbrush. Various bottles of hair mousse, shampoo, soap, and other fluids are seen throughout the course labelled with brands referencing various characters, one of which being labelled Toad Barber, a pun on Toad Harbor. Other objects seen throughout the course include sponges, hula hoops, inflatable balls, bars of soap, a fan, and sunglasses.

Course layout
The starting line is located directly next to a sink full of water. The racers pass the sink before being taken to a fork in the road leading into a bathtub containing a hula hoop. Racers can choose to drive along sponges that lead them into the water, or they can take a ramp to go directly into the tub. After swerving around bath bombs, racers soon drive down the drain. Here, a wedding ring acts as an arch representing an off-road shortcut. After leaving the drain section, racers are on the floor, avoiding soap next to a large fan. Racers then take a Glide Ramp over a toilet, taking them onto a wooden shelf. Serpentining around holes in the shelf, one last glider is used to pass the finish line.

References to the Super Mario franchise
Similarly to the Mario Kart 8 version of, the course contains a number of small references to various games from the Super Mario franchise in the background of the course:
 * A clock resembling a Biddybud (and by extension a Biddybuggy) appears near the starting line.
 * A can of Princess Orange can be seen near the bathtub segment.
 * Stars pattern the bath curtains.
 * The wallpaper of the bathroom, seen most clearly around the bathtub, features the cloud sprite from Super Mario Bros.. The color, too, makes the wallpaper resemble the sky from World 1-1.
 * Lakitu's Cloud can be seen on several balloons.
 * Sunglasses resembling those Princess Peach wears while visiting the Lake Kingdom in Super Mario Odyssey can be seen leaning on top of a suitcase.
 * The aforementioned suitcase has a number of stickers plastered on its side, one of which depicts a Shine Sprite.