Burnt plug on royal coke machine

[Honest Engine]

Was smelling something for a few days and discovered this had happened to my coke machine plug

Any ideas on what could have caused this?

[cvending]

Usually that is caused by a loose connection.  
poor contact will cause arching. I would replace the end of the chord and the wall except I left as well or same think will happen again

[AngryChris]

Loose connection.  Make sure the outlet provides a tight connection and replace the plug.  You might have to cut the cord back if the wires are damaged or you can replace thr entire cord

[OVend]

https://www.homedepot.com/p/Leviton-15-Amp-125-Volt-3-Wire-Plug-Yellow-R10-515PV-0YL/309610976

would recommend one of these

I have installed one myself worked well

[AZVendor]

You probably need to replace the wall outlet too.

[AngryChris]

Oh, and consider yourself very very lucky if all you have to worry about is a bad plug/cord.

[Vendo Mike]

I hope this was not plugged into an extension cord.  This would be a good example of thermal runaway which is a common result when extension cords are used on refrigerated and heated equipment.   I would take a close look at everything that pulls directly on the 115 supply (i.e condensor fan/compressor, evap fans (if 115 VAC), lighting, etc )  to make sure something didn't short causing the issue.