How would Spidey and Mysterio (I'm assuming it's Quentin Beck, not one of the other ones) even work together?
Spidey: I'll take the one on the right, bowl-head, you tackle Ock!
Mysterio: OK, Otto, uh, I'm gonna need you to like... turn around and count to ten? Then I'll make some really, uh.... bitchin' illusions!
Nah, I'm sure he'd have some basic devices on hand, but really. Mysterio is an illusionist. He has no real offensive capabilities. Certainly not able to damage the likes of Dr. Octopus or the Man Beast. The best he could do would be to run interferance for Spidey, try to keep one of the bogies distracted.