I just created this account so I could share what I found out about this issue. I'm trying to share it with as many of you as possible in the hopes that it'll help you out too! But I think I have something that might work. At least for me, it did.
I had this exact same bug happen to me too. After looking around everywhere and not finding much help, I think I finally found a solution to the problem on my own. Based on my testing, it seems to me that this is the only way I can figure out to do it. If you die, the supplies persist in your inventory; you can't drop them, even with god mode / the creative menu; there doesn't seem to be a console command for removing items from your inventory or resetting your inventory. It's really frustrating. But here's what I've found:
I'm playing on Alpha 17 (b240).
1. Make sure that "Cheat Mode" is on under the advanced tab of server / game config before you load the world.
2. Once you're in your world, make sure to remove everything from your inventory (except the supplies, obviously) and store it in a chest or something.
3. Make sure you have admin privileges (I do in my world because I created it; I honestly don't know how much more complicated it might be if you're playing on someone else's server).
- Edit: It looks like if you aren't the administrator of your server, if you can get the server admin to add you as another admin using the "admin add <player name>" command, I think that might help get around this issue.
4. Open the creative menu (for me it's the "u" key, which I think is also the default). You should be able to see your inventory on the right as well as a window full of items you can spawn on the left side.
5. In the bar just above your inventory slots there's a trash can icon which says "Clear Inventory" if you hover over it. Click it.
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That
should fix it for you! I don't think I did anything else of special note, but I did try a lot of other things before finding this solution, so it's possible that something I messed around with enabled this feature by accident. So - if this method doesn't work for you, let me know and hopefully we can figure out what's really going on and sort this out.