Kylie and Kendall Jenner Sing Billie Eilish, Drink Beers in Car Together

Kylie and Kendall Jenner know how to party ... belting out Billie Eilish lyrics and pounding a couple cold ones in a new video posted to social media.

The video went up on Kylie's IG Saturday ... showing her and her older sis as they sing along to Billie's hit song, "L’Amour de Ma Vie" from her newest album. And, ya gotta watch the clip 'cause the ladies have the best time while it plays.

The duo sing along to the lyrics, bouncing around in their seats ... and, even sipping on what look like a couple of Estrella Galicia beers -- nothing like a little buzz to get the party going!

When the song picks up steam, they both start hair-whipping, fist-pumping and clinking their glasses together ... giggling all the while. Their mom Kris makes an appearance too -- though she's not as big on the song, it seems.

It's a great time for the sisters ... who are super tight obviously. They've hit multiple huge events together -- like last year's Met Gala for instance.

Kendall dove deep into her relationship with Kylie in an issue of Vogue published earlier this month ... explaining she and her sis don't compete like many might think -- choosing to encourage one another instead.