Renamed Get It 1st for Summer, the instant-win promotion kicked off in January on six confectionery countlines and targets 16 to 24-year-olds.
From June, it will run across Mars, Snickers, Bounty and Maltesers stick ice creams, as well as the Twix ice cream bar.
The two new star prizes - VW Beetle Cabriolets in new colours with customised number plates - have been selected to appeal particularly to the target audience.
Participants text or log onto the promotional website and then type in the code found on the inside of each wrapper.
They can also collect tokens
to download other freebies, including a range of mobile phone ring tones.
The company said Get It 1st for Summer would benefit from the confectionery promotion’s £5m support budget and would also get dedicated support from online and text messaging, radio ads and point of sale material.
A Masterfoods spokeswoman said the promotion was the first of its kind to run across confectionery and ice cream. She added that it offered consumers “genuine firsts”.