If you thought jeans and a t-shirt was appropriate attire for grabbing lunch with your sister, you clearly haven't seen Kendall and Kylie's latest outfits. Spotted outside of Joan on Third in West Hollywood, CA, the Jenner girls — who recently starred in a very sexy Balmain ad [1] — showed us all how to dine the fashion-girl way.

While Kendall continued to go the plunging neckline route [2] in a lavender jumpsuit, Kylie took a page [3] out of big sis Kim's book in a formfitting tank dress. Read on to see their looks in full, and reconsider reaching for joggers before you head out to brunch this weekend.

Kendall was seen entering the restaurant in a chic halter-neck jumpsuit.

Again, she opted for a low-cut neckline [4] and paired her look with a casual pair of cutout sandals.

The star amped up her look with a few finishing touches, such as a drop necklace, a striped Céline bag, and a pair of aviators.

Kylie also dressed up for lunch, wearing a beige body-con tank dress.

The youngest member of the Kardashian-Jenner crew paired her look with cutout booties from her growing shoe collection [5].

Kylie completed her outfit with a feathered bag and a pair of aviators.