The competition, run in conjunction with Young Creative Network, asked young designers to visualise the future of milk.
It challenged students from across the UK to reinvent the traditional milk bottle from a simple embellishment or graphical overhaul through to a complete structural reinvention.
To create her winning design, Stewart carved a section out of a traditional Cravendale carton and inserted a miniature farm in the space, complete with cows and a Cravendale billboard.
Her prize includes £1,000, a Cravendale award and a placement at a creative agency to help develop her skills.
The first runner-up was by Matthew Durant, featuring a bottle with a bent neck to add a pleasing aesthetic quality at the same time as making pouring of the milk easier and more efficient.
The second runner-up was by Joanna Angles, featuring a smart milk bottle with a freshness indicator that turns from white to red when the milk has gone sour.
Louise Barton, senior brand manager at Cravendale, said: "Cravendale Future Milk was all about challenging the next generation of designers - and consumers - to think about milk completely differently.
"Eleanor's design really appealed to us - as well as being really fun and visually exciting, it had a clear educational aim to help teach kids where milk comes from and why Cravendale is so special."
The competition ran via the brand's for three weeks in July and received more than 300 entries.