  Context: The local census of very low-mass stars and brown dwarfs is crucial
to improving our understanding of the stellar-substellar transition and their
formation history. These objects, known as ultra-cool dwarfs (UCDs), are
essential targets for searches of potentially habitable planets. However, their
detection poses a challenge because of their low luminosity. The Gaia survey
has identified numerous new UCD candidates thanks to its large survey and
precise astrometry.
  Aims: We aim to characterise 60 UCD candidates detected by Gaia in the solar
neighbourhood with a spectroscopic follow-up to confirm that they are UCDs, as
well as to identify peculiarities.
  Methods: We acquired the near-infrared (NIR) spectra of 60 objects using the
SOFI spectrograph between 0.93 and 2.5 microns (R$\sim600$). We identified
their spectral types using a template-matching method. Their binarity is
studied using astrometry and spectral features.
  Results: We confirm that 60 objects in the sample have ultra-cool dwarf
spectral types close to those expected from astrometry. Their NIR spectra
reveal that seven objects could host an unresolved coolest companion and seven
UCDs share the same proper motions as other stars. The characterisation of
these UCDs is part of a coordinated effort to improve our understanding of the
Solar neighbourhood.
