Is it more healthy to mix whisky with water than coke ? which is less damaging to the body? i know all alcohol is bad but this is only a 1 night thing

Doesn't matter.: If truly only for one night, then there are no risks to mixing it with either water or Coke. The alcohol is certainly the ingredient that has the most potential for harm. If used long-term, it would probably be better to mix with water, just to avoid the sugars in the soft drink. However, it is not a good idea to drink whiskey on a regular basis. Good luck, and enjoy your evening. Cheers!