All perfect praise be to Allah, The Lord of The Worlds; and may his blessings and peace be upon our Prophet Mohammad and upon all his family and companions.
Buying and selling those coupons isn`t permissible because the commodity itself isn`t known, and this is called Jihalah(ignorance) sale, as indicated by Al-Khateeb Ash-shirbini who said, "It is a condition in sale that the contracting parties know the item being traded "{Moghni Al-Mohtajj 2/352}.
Also, Islamic Sharia has forbidden selling an item before possessing it for Ibn Abbas(May Allah be pleased with them) reported that the Prophet(PBUH) said, " Whoever buys food, let him not sell it until he has taken full possession of it"{Related by Bukhari&Muslim}.
It is feared that the above transaction is a kind of usury. And Allah knows best.