CE-525 Pilot reported taxiway excursion due to icing.

Narrative

PM (Pilot Monitoring) recorded ATIS information from ZZZ and the PF (Pilot Flying) briefed the approach accordingly. Runway conditions were expected to be wet; and braking reported as 5/5/5. Approach to land was stable; with touchdown occurring within the touchdown zone. Ground flaps and brakes were applied according to CE-525B operating procedures. Braking action was consistent to wet runway conditions with no issues of traction or stopping power as experienced by the PF. PIC (Pilot in Command) requested controls from SIC (Second in Command) to further test the braking action. Prior to the transfer of controls; the aircraft was nearing normal taxi speed. Transfer of controls was made; and the PIC determined the braking was excellent and returned controls to the SIC. (Prior to exiting the runway; a communication from another aircraft was heard on Tower frequency reporting they had clipped taxiway lights and braking nil while exiting at the end of the parallel runway.) PF slowed the aircraft to a near stop and exited the runway at [Taxiway] XX. Once the aircraft was turned and exiting the runway; PF informed the PM that sliding was occurring and there was no directional or stopping control. The aircraft slid laterally and came to a stop with the left main in the grass on the left side of [Taxiway] XX exiting the runway. Break thrust was applied in an attempt to move out of the grass and the aircraft began sliding again; making a left 270 spin. With both engines at idle; the aircraft was again sliding laterally. The left engine was then shut down which stopped the slide. ATC was notified and checklists were performed. The aircraft was towed from XX to [the] hangar where post flight actions were conducted.