Nema 6-15 to nema 5-15 (hot hot ground)
Installed fixtures must be correct

Any receptacle which is installed as part of the building must be exactly what it says on the tin.  If you are provisioning 240V hot hot ground to the receptacle, and breakering it for 15A, it must be a NEMA 6-15.  Period. 

The simple fact is, if you provision 240V to a NEMA 5, it will be a matter of time before someone plugs a 120V appliance into it. You know the feeling, you're trying to get something done, you have a 5-15 plug in your hands and you search for the nearest receptacle your cord will reach.  Everyone else does the same thing. And that's the problem. Your rush to an immediate goal is no excuse.    A reasonable person will foresee that a miswired NEMA 5 will find a victim, just a matter of time.  An exacerbating factor is that you're intentionally refusing to pull a permit and get inspected because you know you'll flunk.  

Just don't do it.  Seriously.  Not meaning to be a nag here, just there's a better way to do that thing. 

The cheater is the way to go

None of this is legal.  But since it's not part of the building, the AHJ (building inspector) doesn't have nearly as much to say about it. 

A 6" long homemade extension cord will send signals that makes it far less likely for an innocent person to have an accident.  First, there's no logical reason for a 6" extension cord to exist.  Second, it's obvious that the plug is weird, *presuming that you use a NEMA L6-15 locking type.  Also, label it clearly, and attach it securely to the charger with a cord coupler.