Most people know how strict is Australian quarantine at airports and people are not allowed to bring any unprocessed food. But that is not it. All traveller should be aware about interstate quarantine. To avoid spread pests, diseases and weeds from one part of Australia to another there are restrictions what you can take from one state to another, or even from one part to another place in the same state. I never saw inspectors on the road, but better to be prepared and not to buy restricted food (especially fresh fruits) before crossing one of interstate or quarantine borders. Traveller’s guide to Australian interstate quarantine can be found here.