This was one of the baby android challenges. We can solve this in just 5 min.
We get an APK file in the challenge zip.
Decompile the apk with apktool
This can vary depending on the challenge, but we just searched for any string matching "flag" and got interesting results
After quick analysis of the SMALI file we can see that the app is using base64 on a hardcoded string we can try to just decode it
Searching for the string in the file and then decoding it, gave us the flag.
pCTF{7hr0w_4aPpl3_fr0m_w1nDoW}