To cite sundialr in publications use:

Satyaprakash Nayak (2023) The sundialr package: An Interface to 'SUNDIALS' Ordinary Differential Equation (ODE) Solvers. https://doi.org/10.5281/zenodo.5501631/

Corresponding BibTeX entry:

  @Misc{,
    title = {The sundialr package: An Interface to 'SUNDIALS' Ordinary
      Differential Equation (ODE) Solvers},
    year = {2023},
    author = {Satyaprakash Nayak},
    doi = {10.5281/zenodo.5501631},
    url = {https://github.com/sn248/sundialr/},
  }