Hitler accidentally shooting his pink pistol with his girlfriend's pink pistol. He died soon after.
Hitler boards one of the navalised P.1100 Unterseepanzerkampfwagens, designed to ford the Channel with their 75-metre schnorkels, for a demonstration.
A seam fails because of imperfect fits between the prefabricated sections of the tank. It floods and everyone drowns. The dignitaries on the shore are still waiting.
After the failed beerhall coup, Hitler goes to prision as in OTL. There he becomes someone's bitch and catches sypillis. He's given mercury to "treat" it. The rest writes itself.
Hitler goes to Sea World and gets anal raped to death by a dolphin.