There is something for everyone, from car customization to training options. The majority of these are included with the mod known as Bakkesmod.

What is Bakkesmod, exactly?
Bakkesmod is a third-party mod that enhances the gameplay of Rocket League by adding new features. While the items are only visible to the player who created them and cannot be seen by other players, it is a useful feature for testing out items or using combinations that are not currently available in-game, such as a completely black or white car.

The possibilities are virtually limitless, as anyone with coding experience can create a plugin for their own use.

How to set up Bakkesmod
Simply download the installation file and sit back and watch the software do its thing. This is available for both the Steam version and the Epic Games version. When It Comes to Rocket League, What Is the Best Car? 

What plugins should I use?
To discuss all of the available plugins would require a novel, so we'll limit ourselves to just ten plugins that we think are particularly good.

Bakkesmod's AlphaConsole can be found here.

TOP 100 Rocket League Goals & Funny Moments #4rocketprices.com

Henk Highlights #16 | I lost everything...rocketprices.com

This mod used to be a separate mod and even a little competition to Bakkesmod, as it shared many of the same features as the latter.

Statistical data from RocketStats.

The statistics for the current session may be of interest to those who are playing in order to advance in rank.