Kardashians -- Secret Deal with Adidas?

Khloe Kardashian was head to toe in Adidas over the weekend, which makes sense given boyfriend James Harden's $200 million deal with the company ... but now it seems the entire clan is in on the act.

Kylie was out with Tyga Sunday in Calabasas, decked out in an Adidas tracksuit, and this isn't the first time they've been spotted giving the company prized promotion.

It would sure make sense. Fact is, they might be better pitch people than Harden.