Not sure but long time ago, people are talking about using WPE Pro and CCProxy to modify traffic from bluestack. I used it once, trying to filter all normal daily chest to become high rare chest. But really, it's not that simple. Since the traffic may be encrypted with MD5, CRC32, the encrypt key is changing every minutes, so it is pointless.
One more rumor, it is using BurpSuite (my favourite network poisoning tool) and use a Proxy tool to redirect https to http and send the traffic to burpsuite to manipulate. BurpSuite is a dangerous tool and it is really complicated, you can even hack a server side game using burpsuite with no doubt but again, do it carefully or you will get banned.
P/S: to hack a server side game, it is pointless to do memory hack. It is smarter to modify network traffic sending to game server