The best way to avoid the wet look is to ensure the printed icing sheets / cake toppers are applied to a cake at room temperature NOT a cake straight out of the fridge. Another major cause is keeping your cake in an air tight container which can result in your cake sweating and moisture developing on top of the icing sheet / cake topper.
You should avoid putting icing sheets directly onto cakes that have come out of the fridge or the moisture comes up through the icing sheet and leaves like a “morning dew” on them! This also applies to fresh cream – the moisture / cold comes up.
The icing sheets should be applied onto room temperature cakes, so no matter what the cake is covered in; buttercream, fondant, chocolate, ganache etc… it needs to be room temperature or you will get the dew effect.