Unlock career reward outfits

I assume you mean other than actually playing through the career?

There's a couple ways you can do it. There are mods that will just unlock them for you for all played sims.

A way to do it without mods is to download a sim from the gallery which has them all unlocked already. Merge them into the household in your game where you want them unlocked. Once merged, the household has the outfits and you can remove the sim. Searching Hashtag: #CASUnlocks should find you a few options for this.