Thinly slice cucumbers using a mandoline or sharp knife.
Add cucumbers to a container with a tight-fitting lid.
Add sugar, MSG, sesame oil, chilli crunch, soy sauce, fish sauce, furikake, sesame seeds, and grated garlic if using.
Seal container and shake well to distribute everything evenly.
Taste and adjust seasonings as needed.
Serve immediately or chill for 15-20 minutes to let flavors meld.
Best eaten within a few hours before cucumbers soften.