Well, the senior British commander at Singapore, General Percival, spent most of his wartime imprisonment at the hands of the Japanese in a camp in Manchuria. He and his men were subjects in Japanese medical experiments.
Generally the generals were treated the same way as other officers by both Germans and Japanese, though of course there were substantially different atitudes to the concepts of POW's by these Axis countries.
The British also treated captured generals in the same way as other officers. Arnim was allowed to surrender and retain his sword (in recognition of Arnim being involved in saving the lives of sick British POW's) whilst Italian generals were content to sit out the war in whatever camps the British put them in.
The Soviets used captured generals such as von Paulus as willing participants in anti-fascist propaganda.
''Give me a Ping and one Ping only'' - Sean Connery.