Massive in Japan, less popular in the UK. We have never found them to be hugely exciting as the soda water often dilutes the whisky too much - perhaps that's why they're big in Japan. Simple solution - add a shot of shrub, it lends a whole new dimension and brings all that whisky flavour out.
150ml soda water
- Measure shrub and scotch into glass
- Add ice
- Top with soda water
- Stir well