If you're holding something which sticks to your hand, like a ping pong paddle, microphone, or a maker pen, you can release it from your hand by pressing:
- PSVR: Square or Triangle button
- Oculus: Y or B button
- Vive: Menu button
- Index: B button
- WMR: Menu button
For a full review of the different button bindings for every VR device, please see this article.