Some major restaurant chains in Hong Kong are offering discounted cash coupons to attract customers in a sluggish market, but the city’s consumer watchdog has warned people to check the terms carefully and buy only what they genuinely need. Tai Hing, a leading casual dining group with 19 brands, launched promotions earlier this month to mark the second anniversary of its mobile app. Customers who bought HK$1,000 (US$129) worth of coupons between October 9 and 20 received 23 cash coupons valued...