There are such a variety of individual experiences it's almost impossible to provide a single answer. The most common results of being fired was either you went home, or you went to some useless backwater posting.

Take for example General Walter Short, of the US army. He was a major (two-star) general. He was appointed to the Hawaii command. That came with it a (temporary) promotion to lieutenant (three-star) general. After Pearl Harbor he was demoted back to his permanent rank. Which wasn't really a demotion, as it had only been assigned on a temporary basis. But it was a bit of a slap in the face, as had he had a more "successful" tour he almost certainly would have seen his promotion made permanent. He was allowed (forced) to retire, and was eased into a decent but not great position at Ford. How culpable Short was for Pearl Harbor, could be (and has been) hotly debated. But he was given the gold watch, the retirement party and quietly shuffled out of the way with a certain amount of dignity.

When George Patton was relieved of command, he didn't even get demoted. He was just put in Eisenhower's dog house for a year and then given command of Third Army. In the meantime he was used as a decoy to distract the Germans.

Those demonstrate the US way. Sacked generals were retired out, or shuffled to insignificant commands. If they were otherwise quite good, they might earn a chance to command significant units again.

That's also how it worked in most of the other armies. Fired generals went to insignificant commands, or went home. Gerd von Rundstedt was famously fired three times by Hitler, and brought back twice because he was too good a talent to leave sitting at home. Of course that's where he was when the Allies found him and arrested him, Hitler having fired him for the third time in March 1945. That wasn't uncommon; most of the best known German generals were fired at least once, and most of them usually didn't languish in civilian life for long before being recalled.

The Soviets on the other hand were much harsher to commanders who were fired. I'm not aware of a single Soviet general who simply went home. Instead fired generals met a firing line. Or alternatively they got almost certain death by being given command of a penal battalion and forced to fight in the front lines. Over 200 Soviet generals died this way, and I'm talking strictly post purge. Stalin didn't screw around. Dead generals tended to leave the other generals highly motivated. And Stalin certainly provided plenty of examples to encourage the others.

The two commanders at Pearl Harbor at the time of the attack, Lieutenant General Walter Short and Admiral Husband Kimmel, were both blamed (perhaps unfairly, but that's for another day) for the results of the bombing.

Short was removed from command of the Hawaiian Department and ordered back to Washington. He was also reduced back to his permanent grade of Major General. He retired from the Army a few months later.

Admiral Kimmel was found to be derelict in his duties, relieved of command 10 days after the attack and reduced to Rear Admiral. He, too, retired in early 1942.

As a follow-up what caused them to get sacked? Does this include the Japanese generals.