Kim and Kourtney Kardashian Fight Over Kids' Birthday Party: 'This Is Not About Your Brand!'

Planning North and Penelope's joint Candyland-themed birthday party went from sweet to sour real quick for sisters Kim and Kourtney Kardashian.

In a new sneak peek at Sunday's new episode of "Keeping Up with the Kardashians," the two get frustrated with each other as they battle over what kind of candy to get for the bash. Yes, this is the kind of stuff they argue about now.

Right off the bat, Kourtney said she wants to try and keep the celebration "somewhat healthy," something Kim believed was downright impossible for a party centered around sugar-filled confections.

"It's not going to be healthy no matter what, sugar's not healthy, but let's not do the nasty stuff with food coloring and gross shit," said Kourt, who then suggests getting "organic cotton candy."

"Kourtney has this vision of no sugar, no disgusting chemicals," Kim vented in a confessional. "It's like a completely sugar-free, gluten-free, party-free, fun-free zone because Kourtney has decided that does not make sense. That's really not the theme of what North and Penelope wanted for their birthday."

As Kourtney continued to rail against products made with "food coloring that gives people diseases," she added that her "brand is not unhealthy." That triggered Kim, who shot back, "This is about a kids party, this is not about your brand!"

Kim then attempted to call out her sister's hypocrisy for her causes, saying, "Why does your car have leather seats, why are you wearing plastic glasses?"

In her own confessional, Kourtney was incredulous that Kim was "not willing to compromise" and didn't feel "guilty" about giving all the children at the party "so much junk." She said her sister was working with "such a dated vibe" all around.

"I want a fun kids party with real candy," Kim told her, simply. Replied Kourtney, "Well, that's your problem."

"Keeping Up with the Kardashians" airs Sundays on E!