Is it illegal for merchants to sell hotel mineral water and return one yuan? How to complain?

It is illegal for merchants to sell hotel mineral water back to one yuan. The merchant sells mineral water to the hotel and promises to return one yuan, but fails to honor the promise, then this constitutes fraud. You can complain to the local consumer association, the administrative department for industry and commerce or other relevant departments. The specific complaint process may vary from region to region. Please check the local consumer rights protection channels first, or consult local consumer organizations or law firms for more accurate complaint guidance and suggestions. You need to provide relevant evidence materials, such as purchase vouchers, transaction records, contracts, etc. , so that relevant departments can verify and handle your complaints.