I was looking to purchase a ticket for an international flight…and after comparing prices extensively, I came to realise, at least on BudgetAir.com.au that when I had the ShopBack notifier activated, the price of the same ticket was at least $40 higher than when it was turned off (thus negating the $6.50 cashback). So I went hunting for a coupon code and found this one that worked when I bought the ticket. Just enter into the Discount Code field on checkout.
The page I've linked to reads: Valid for travel on select dates. Destinations include Delhi, London, Auckland, Singapore, Bali and more. T&Cs apply.
However I dont know what the T&C's are or the selected dates or if there are any specific limitations on the locations (as that's all the information that is on the page). It worked for me when buying a one way from Delhi to Sydney.
Mod: Updated link directly to the promotion.
Is that enough to buy a bottle of water on the flight?