Little seems to have been written about how the European and Asian Axis Powers helped eachother or at least tried to against the Allies, who worked as a coordinated coalition. I know that during the 1930s Germany tried to make pacts with both Japan and China, but beyond Hitler's deceleration of war against the United States after Pearl Harbour I don't know of any transfer of materials, technology or intelligence etc between Tokyo and Berlin. Was this simply an alliance on paper or not?
From a practical standpoint it was very difficult for Germany and Japan to provide any substantial amount of mutual aid given that both the Suez Canal and Panama Canal were under Allied control. However, there were a handful of technology transfer missions between the two, which had to go around the Cape of Good Hope.
Among the things that Japan sent were blueprints for the Type 91 aerial drop torpedo and the Type 95 oxygen torpedo. Germany sent things like plans and components for radars and engines, including blueprints for the Me 262 though the submarine carrying that last one (I-29) was sunk before returning to Japan. Germany also sent U-511 which was then brought into the Imperial Japanese Navy as Ro-500 and mostly for testing and training.