At some level Germany was trying to get Japan to put boots on the ground in Sibera and the Soviet frontier- it'd cause problems for one of the primary Lend Lease supply routes- but that never really lead to anything. Japan had a hard enough time getting anything meaningful done in China, let alone raising more troops to go after what may very well be the worst parts of the Union in terms of logistics and weather and terrain.

There was also some limited technology exchange (or at least a hand-me-down) between Germany and Japan. Japan was working on an experimental rocket fighter prior to their surrender which was based heavily on German prototypes and concepts.