Can you sell supplies?

[SgtFrog]

If I'm primarily a drone-using ship (Engi A or B, for example), I don't need 26 missiles, right? I wish I could sell a few of them. If I had a Heal, Fire, or Small Bomb, I'd keep them, but on this particular run, I did not.

[The Captain]

You can only sell or trade them in certain encounters which aren't labeled. You hit a beacon and get offered a deal, and it may not be a deal you want.

[UltraMantis]

You can never sell supplies though you can trade them in special encounters. They cost you nothing and take no space and who knows, you may run low on drones and find a missile launcher. But usually you will find yourself with an overabundance of one supply type. It's how the game is.