Rockstar Games promised a reward if players managed to steal a bunch of money in GTA Online and both sides delivered, resulting in some free cars for everyone.
GTA Online players can claim two cars for free until December 30, 2020. Technically, the Brioso 300 is the only one that will be free until that point in time while it's currently unknown how long the offer for Sentinel Classic will last.
You can find both of the cars on the Southern San Andreas Super Autos in-game website but the prerequisites for obtaining each are different. In the case of Brioso, everyone can claim the car at no cost as it's the vehicle that is featured with this year's Christmas promotion.
Meanwhile, Sentinel Classic is available for free only to the Twitch Prime / Prime Gaming subscribers who have linked their Amazon and Rockstar Games accounts.
As for the cars' performance and regular prices, both are somewhat expensive, although you can grab them both for roughly GTA$ 1 million since Sentinel Classic's trade price is GTA$ 487,500 or GTA$ 650,000 with regular price. Brioso normally costs GTA$ 610,000 but it's down to GTA$ 457,000 with the trade price.
In case you are not familiar with the term, trade price usually refers to completing a heist under certain circumstances. Sentinel Classic gets discounted if you use it as a getaway car in The Diamond Casino heist finale while Brioso is discounted after completing the Cayo Perico heist as a leader.
Either way, it's better to pick these up for free and when you tally up the trade price costs, you will still save GTA$ 944,500 by obtaining them for free.