Kendall Jenner isn't just a skinny supermodel, she's an athletic girl with a toned tummy and a killer bod!

We caught up with the young cover girl Friday at her new favorite spot, Alfred's Coffee, where she picked up a bottle of water for hydration after he coffee (smart!).

Jenner's rolling solo right now, after a romantic vacay with boyfriend Harry Styles in St. Barth -- in fact, half-sister Khloe confirmed the young couple's relationship in a recent interview, "Do I think they're dating? Yes. I don't know if they're like boyfriend-girlfriend. Nowadays I don't know. People are weird with stuff. So, I don't know their title. But I mean, they were in St. Barts together hanging out, so to me that's dating."

She must be missing her man!