"Unnecessary junk" refers to things or items that are not needed or useful. It implies that these things take up space or clutter our surroundings without serving any practical purpose. Full definition
That way, we spend less if at all and don't end up with more unnecessary junk! (almafied.com)
If you decide to just throw in the towel and pig out on unnecessary junk food while on vacation, you may suffer the consequences, especially if you are used to eating healthy. (westonaprice.org)