A website, an app, a repo on Github. If the answer to that question is 'No' then my assumption is either a) this person isn't interested in the work, or b) they don't know how to code in the real world and I'll be paying them to learn.
I'm constantly amazed at the number of people applying for dev positions who claim years of experience and have absolutely nothing tangible to point out.
I run a small operation so I can't comment on big firms.
TLDR: Build something recruiters can see, and preferably use. It'll put you instantly in the top 10% of applicants.