Maybe they are reusing a html template for their competitions and forgot to remove that part. Their past competitions clearly state whether a purchase is required. T&Cs don't mention anything about a purchase for this competition so just ignore it.
Win a Cutlery Set Valued at over $150 from FoodWorks
5
Dates
Closing Date
07/06/2016 11:59pm
Prizes
Description
1x Cutlery Set
No. of Prizes
1
Total Prize Pool
$150.00
Entry Requirements
Open To
Australia-wide
Entry Limit
One per person
Entry Methods
Website
Prerequisites
n/a
"For your chance to win, simply tell us your favourite tip for cooking the perfect rice"
Winner will be announced Wednesday June 8th
Related Stores
The page implies that it requires a purchase. I suppose if you won and they asked for your receipt you could go out and buy some.