The HyDRA challenge is meant to kick off such a systematic approach to microhydration, with numerous conceivable follow-up options. HyDRA stands for Hydrate Donor Redshift Anticipation, where redshift refers to the wavenumber downshift of the donor OH vibration relative to the symmetric stretching fundamental of the water molecule at 3657 cm -1 . The switch between absolute values and relative trends is thus trivial in this case, because it only involves adding or subtracting this experimental monomer value. In the present work, we use the sign convention that a positive downshift describes a lower wavenumber in the complex than in monomeric water. Here, we outline the construction of an initial training and test set for neutral organic monohydrates which was recently offered to theory groups , connected with the invitation to participate in a blind challenge.