Modified from an earlier answer of mine on Japanese-German cooperation.

There was generally next to no functional military cooperation between the Japanese and the Germans during the war. There were technical exchanges, trade, and a German group of U-boats that operated out of Penang (the Monsun Gruppe ), but that was about the limit of Axis cooperation. The sheer geographic separation as well as the differing strategic priorities of each Axis partner rendered the alliance dysfunctional at the best of times.

The Japanese inaction against Siberia throughout the war was a case in point in how there was a fundamental lack of cooperation. The IJA had already fought two sharp border conflicts with the Soviets in 1938 and 1939 which showed the shortcomings of the IJA as a modern force. The swift fall of France in 1940 further underscored to the IJN the need to modernize its forces. The problem the existing Japanese empire did not possess the resources needed for such a modernization. This led the IJA to adapt elements of the IJN's Nanshin (southern drive) to seize the resources of Southeast Asia for modernization as well as cut of the KMT from Western supplies. Ironically, while planning for Barbarossa, Germany's Japanese policy encouraged this reorientation with the logic that Japan occupying these areas would deny them to the UK and entangle American naval power in the Pacific. Tokyo was largely kept in the dark about the Soviet invasion despite the Tripartite Pact. Although Barbarossa did encourage some hotheads in the Kwantung Army to propose a Siberian attack, realists in the IJA's General Staff prevail because there were significant doubts that Japan had the capability to invade and hold Soviet territory without the Southern Resources Area (the term for SEA among both services). Germany's push for a Japanese Siberian invasion only picked up steam after Barbarossa had stalled, by which time the die had been cast for the Nanshin. Although some in the IJA conceived of a later invasion of Siberia once the Pacific War had been won, the war proved a bottomless sink of men and material that prevented any expansion northward, and all plans for a Soviet war became postponed indefinitely.

The trading relationship between the Axis partners also showed a similar pattern of short-sighted policies and different priorities. For the most part, technology and trade in raw materials between Germany and Japan occurred through individual blockade-runners. In exchange for examples of German military technology and plans, the Japanese provided raw materials and other items the Allied blockade prevented from being imported to Germany. From the outbreak of the war to around 1942, surface ships formed the bulk of inter-Axis trade. Of some 104,232 tons of raw materials shipped from East Asia to Europe in 1941-42, approximately 75,000 tons arrived in European ports. The Germans and their Italian allies did not make the most of this brief lifeline and the items ordered from Japan included non-essential materials like tea and coffee and cooking oils. Although these raw material helped ease domestic shortages, it exemplified the skewed and myopic priorities of Italy and Germany. The nature of industrial warfare necessitated a more ruthless prioritization, especially given the acute shortages of strategic materials like rubber and tungsten. This short-sightedness came to a fore by 1942 when Allied naval superiority was able to cut the surface blockade-running lines with ease. Although there were tentative steps towards an aerial connection between East Asia and Europe, the only practical option for the Axis to run the blockade was submarines. German Type IX U-boats could carry at best 2-3% of the tonnage of a surface blockade-runner and the larger Japanese submarines were only slightly better. The inability of the European Axis to prioritize their brief window of opportunity in 1941-42 of building up stockpiles of East Asian raw materials led to persistent shortfalls of these materials in the German war economy and their substitution by inferior ersatz ones.

Much of the exchanges were not on the scale of Lend-Lease but involved single examples of materials. Most of these sales focused on German to Japan technical exchanges. For example, the German victories in 1940 and 1941 had underscored to the Japanese the importance of tanks to modern warfare as well as Japan's inferiority in this field. Germany though was less than forthcoming on this matter. Germany sold Japan two semi-obsolete PzKpfw III tanks in 1943 which made their way to Japan by blockade-runner. Japan also bought copies of both a Tiger and Panther, but these tanks were too large and difficult to ship, so Japan never received them. Japan had more luck with smaller items such as the MG 151 autocannon, eight hundred of which arrived on the Italian submarine Cappellini in 1943. The Germans also did sell Japan individual examples of aircraft. This was in keeping with prewar practices in which Japan bought advanced aircraft to glean both technical secrets and to compare with Japan's own domestic planes. Japan received both an BF-109E, FW-190, and Me-210 during the war. There were also attempts to send Japan examples of both the the Me-262 and Me-163 along with detailed blueprints, but the Allied blockade sank the submarines carrying this equipment. Japanese attaches were also privy to German some technical secrets and this informed the Japanese effort to produce rocket and jet aircraft late in the war. The resulting Nakajima Kikka and Mitsubishi J8M were the result of this game of telephone whereby European-based reports describing the German aircraft filtered back to Japan to result in aircraft that sort of looked like their German counterparts.

The Germans showed very little interest in Japanese equipment. Although the Japanese gave the German attaches what was unprecedented access to IJN ships like the aircraft carrier Akagi, the Japanese concerns for secrecy meant the Kriegsmarine officials gleaned little of importance in these tours. There was little IJN influence on Germany's planned superbattleships or aircraft carriers. There are a number of claims that the Luftwaffe was interested in licensed production of the Ki-46 reconnaissance aircraft, but this is unlikely and unsubstantiated. A number of German attache reports back from Japan have an undercurrent of patronizing racism, so it is not surprising that the Germans thought there was little the Japanese produced that was of value to Germany. The only significant instance in which the Germans sought out Japanese expertise was i the planning for Operation Hercules- the invasion of Malta- in which IJA and IJN attaches were present at some of the conferences planing for the abortive invasion of the island.

Payment for technical exchanges was a source of consistent tension within the alliance. The Japanese would pay for German plans and examples of technical equipment with raw materials supplemented by gold, but the Germans would seldom agree on the Japanese exchange ratio for these goods. The disagreement over payment and equitable exchange spilled over into operational matters. The Kriegsmarine ordered the commanders of the Monsun Gruppe of U-boats based in Malaysia to hide the existence of the newly-developed acoustic T-5 homing torpedo from their Japanese hosts or give them an explanation of its technical workings. German industrial firms also expressed grave reservations about handing over plans and other industrial information without first getting guarantees of honoring German patents. There were a few notable instances of fruitful collaboration, such as in 1943 when Luftwaffe general Erhard Milch circumvented the Kriegsmarine and approached the IJN attache Abe Katsuo if the IJN could ship tungsten in exchange for plans for radio-controlled bombs and more examples of Luftwaffe autocannon. The IJN agreed to this transfer and the submarine I-29 delivered the tungsten to Lorient in March 1944 and Milch provided the equipment as payment in kind without hassling over the exchange ratio.

But this type of cooperation was the exception rather than the rule and the inter-Axis trade relationship was characterized by mutual distrust, skewed priorities, interagency rivalries, and miscommunications.

Sources

Barnhart, Michael A. Japan Prepares for Total War: The Search for Economic Security, 1919-1941. Ithaca: Cornell University Press, 1987.

Krug, Hans-Joachim. Reluctant Allies: German-Japanese Naval Relations in World War II. Annapolis, Md: Naval Institute Press, 2001.

Militärgeschichtliches Forschungsamt. Germany and the Second World War Volume VI, The global war: widening of the conflict into a world war and the shift of the Iniative 1941-1943 Oxford: Clarendon Press, 2001.