Whisk:

• 1/4 cup rice vinegar
• 2 teaspoons sugar
• 1 teaspoon soy sauce
• 1 teaspoon fish sauce
• Some red pepper flakes

Then toss in some sliced vegetables. Suggestions include:

• cucumbers
• carrots
• onions
• radishes

Mix, cover and chill in fridge for at least 30 minutes before using.