The Keeping Up With The Kardashians stars dressed down for their sweet treat stop in Beverly Hills on Tuesday, 28 April.
Kendall, 19, is just back home after a quick visit to New York where she partied up a storm for pal Gigi Hadid's birthday and completed a photoshoot for Vogue magazine.
Yesterday, the teenage sisters were back to work together, attending a meeting for a new fashion design project they're collaborating on.
Kylie teased the venture via Instagram, sharing pictures of the girls at work.
Her caption read: designing. I've never been more excited for what's to come! Stay tuned this summer.
(Can we say, they don't look too excited in the picture though, right?!)
Kendall and Kylie are no strangers to design: they have a collection with PacSun, a shoe and handbag line for Steve Madden, a jewellery line, and nail polishes with OPI.
It was confirmed earlier this year Kendall and Kylie are also working on a Topshop range. In a statement, they said: "Topshop to be the exclusive global stockist of the KENDALL & KYLIE young contemporary collection. A collection designed by sisters Kendall and Kylie Jenner will be stocked exclusively at selected Topshop stores globally and online at TOPSHOP.COM.
"Launching for Summer 2015 the collection will comprise a capsule summer wardrobe, characterised by the girls' LA lifestyle and their contemporary, eclectic design aesthetic."