用餐前请出示此卷 用英语怎么说

Please show this voucher to us before your order next time.
Voucher 是最准确的，表示所有类型的“代金券”，包括发票，缴费单都可以这么说，英国人很常用。

用餐前清出示此卷
Please show the coupon before meal.

coupon 一般表示赠券或优惠券，不用ticket

饭前要洗手
You should wash your hands before meal

Show this ticket before meal

Show the voucher before having meals