Ukraine would sell even its nuclear bomb if they still had it, thank God it was taken away from them. But there are rumours that Ukraine did sell two or three nuclear bombs in the 90’s. 25 years have passed, maybe they do not explode any more, maybe they do.
Conspiracy theory. Under the Budapest memorandum in 1994, Ukraine promised to remove all Soviet-era nuclear weapons from its territory, send them to disarmament facilities in Russia, and sign the Nuclear Nonproliferation Treaty. Ukraine kept these promises.
In return, Russia, the United Kingdom, and the United States promised that none of them would ever threaten or use force against the territorial integrity or political independence of Ukraine. They also pledged that none of them would ever use economic coercion to subordinate Ukraine to their own interest.
They specifically pledged they would refrain from making each other's territory the object of military occupation or engage in other uses of force in violation of international law.