In three dimensions,how can i transfom a doughnut shape into sphere without ripping through it?

From a purely practical viewpoint, if your doughnut shape is a solid torus and is made of sufficiently malleable material you can just hammer it until the hole in the middle closes then keep bashing away until you have changed the shape to a sphere. If your doughnut shape is a hollow lump (like a jam doughnut) then it's much trickier but if its made of a metal with a reasonably low melting point you might be able to strongly charge the doughnut inside an evacuated spherical mold then almost melt it and have it deform without puncturing the shell.