Write into stdin of other container in pod using sidecar

Question

For a current project I'd like to write into a process inside my game server container from a sidecar container in the same pod. I already found a solution to serve logs via http using my sidecar application, but writing a process itself is another hurdle.

My testing manifest:

kind: Pod
metadata:
  name: minecraft-server
spec:
  shareProcessNamespace: true
  volumes:
    - name: shared-logs
      emptyDir: {}
  containers:
    - name: minecraft-server
      image: itzg/minecraft-server
      env:
        - name: EULA
          value: "TRUE"
      volumeMounts:
        - mountPath: /data/logs
          name: shared-logs
    - name: testing-gameserver-sidecar
      image: testing/gameserver-sidecar
      imagePullPolicy: Never
      volumeMounts:
        - mountPath: /data/logs
          name: shared-logs

I've already tried accessing the process directly using the shareProcessNamespace property - but I don't have permissions to access the file-descriptors itself.

TL;DR: Is there a possibility to write into the process stdin of the other container in a pod?