Mix garlic and spring onion with all ingredients, except cucumber, in bowl or deep plate that is not too wide. Allow ingredients to sit for a few minutes allowing sugar to dissolve and chillies to moisten.
Cut cucumber into small strips 5cm long and 0.5cm in width. Mix well allowing liquid to cover cucumber. Let stand for a minute and mix again. Serve immediately after, as too much soy sauce will be absorbed in the cucumber if sits longer than 10 minutes making them too salty.