Nick Cannon & Christina Milian Together but Not Dating

Nick Cannon can't stop, won't stop ... hanging with exes, and Christina Milian is the latest!

The former couple was leaving Sugarfish Monday in Studio City where they were all smiles. Christina says they're still friends and working on some business deal.

As for any chance of Nick reconciling with Mariah -- since they've also been hanging out A LOT lately -- listen and judge for yourself.

BTW ... Nick's had a tough time recently in the medical department, but is this guy ripped, or what?