I once had an insider tell me years ago that the girls did a demo of Meghan Trainor's "Walkashame" with Lauren singing the chorus. I'm not sure how true it is, but they were a part of leaks5h and would tell me about stuff before leaks5h actually posted it, they even told me stuff about the That's My Girl video before it came out, so I think it's legit. It's also backed up the fact that in her new book, Ally talks about how they struggled to not have a song about a one night stand be released as a single from their first album:
"We had some serious questions about the song's theme, which was about a girl's walk of shame, home from a drunken one-night stand. Again, most of the girls in our group were still pretty young," Ally writes. "It seemed way too adult for us. We let our management know we didn't feel comfortable with the lyrics, and they told the label." Despite pushback from the label—"The response was, basically: If we'd wanted to sign a Christian group, we would have signed a Christian group."—and waffling from the other girls in the face of such a response, Ally held her ground. The song was eventually dropped. "I was so beyond relieved," she writes, "I started crying."
https://www.eonline.com/news/1197490/the-biggest-bombshells-from-ally-brookes-memoir-finding-your-harmony
Also, the girls revealed to an australian radio station that they did a demo with Sia that ended up going to Shakira which was most likely "Try Everything":
The insider told me: They also almost signed a deal with Google for the Reflection album which, had it gone through, would have included the release of either "No way" (which we know Lauren fought to get released) or another unreleased song called "I Almost Loved You."
We know that they did a demo's for Prince Royce's "Double Vision" and Jason Derulo's "Better With You," I'm DYING to know what other songs by different artists they demoed and of all the unreleased/alternate content we don't even know about!!!