Honestly, I too would not use sheetrock.
I would use rigid insulation and clad the interior with FRP. Fiber Reinforced Panels aka Marlite. This stuff is typically used in kitchens for an easy to clean surface. It is also similar to bathroom shower panels.
An expensive option for the whole shed but THE best option for the wet wall.
To the OP, I am not a fan of drywall in any sort of utility area as it is so easily dinged, dented, or soaked and it has less than a 40# load capacity. Look at the thin fibrous cement panels (normally Hardie Panel). With no interior dimension exceeding 10' there would be no seams except the corners and one horizontal or two vertical per wall. The corners can be either caulked or covered in 1/2" quarter round. If you can accurately measure, including checking for square, you are looking at 2-3 cuts per wall.