Free tickets when you sign up to the newsletter at PBExpo.com.au. You get a free expo bag on entry which typically contains free samples, plus there's always free entertainment for the kids.
Get a free baby bottle at the Closer to Nature stand - available to the first 200 each day. This was advertised on the Closer to Nature facebook page - https://www.facebook.com/closertonaturebaby
They typically have offers like this scattered throughout, offered by various stalls.
not just sydney - https://www.ozbargain.com.au/node/96377 :)