Neutron stars are formed when a massive star runs out of fuel and collapses. The very central region of the star – the core – collapses, crushing together every proton and electron into a neutron.
A neutron star has a density 3 E^17 kg/m^3. One sugar cube is half an inch (1.27 cm) long per side. Which makes the volume of the sugar cube to be 2.05 E^-6 m^3. If the sugar cube has the density of a neutron star, the total mass it should contain is 615 billion kg.
