i believe i was unfairly terminated, what can i do about it?

I am not sure why the other poster was so harsh. Your post to me does not say that you are lazy. Anyway, you really don't have recourse. The employer may have not liked you for some reason or another, or perhaps he was not satisfied with your performance. Just take what you can learn from this incident and move on. I understand why you are upset, but honestly, Dairy Queen is not the best job anyway.

In Canada, when you're fired without just cause (and accepting a single expired coupon would be extremely unlikely to constitute just cause), you're entitled to "notice" or pay in lieu thereof. As to the question of 'how much', that depends on a few things. Provincial legislation has minimum standards, but in addition to that there can be contractual or common law entitlements - in the absence of a contractual termination clause specifying the notice you're entitled to, you're entitled to "reasonable notice". There's no formula, but it's calculated based on factors such as your age, length of service, character of employment, and availability of replacement employment. Working at DQ will seldom give somebody significant entitlements on termination. Most employees are young persons with no more than a couple years of service, if that, and would have their entitlements to notice of termination measured in single-digit weeks.

You weren't unfairly terminated. You got fired for screwing up, accidentally or by negligence.