Simple is best when communicating to a gas-using population. You're really trying to say your car is totally electric and does not use gas, so a sticker with the outlet picture with any variable of the "no gas" verbiage could work. Of course there's "I'm 100% electric," but it falls short for the audience:
"I'm a no-gas EV."
"I'm totally electric; I don't use gas."
"Totally electric & gas-free."
"All electric, no gas."
"Completely electric, gas-free."
etc., etc.,...
I continue to have discussions where I've responded "electric" repeatedly and the gas questions keep coming (they're probably thinking "hybrid," it's all they know here). The point just doesn't get across, unless I say the actual words, "no gas."
Last week, I showed my car to an old friend and said it was a totally electric Nissan LEAF. I popped the charge port cover and opened the L2 port lid to show where I plug in, explaining our lack of fast charging infrastructure for using the QC charging port. She apparently wasn't listening, because she immediately asked if that port was "for when I needed gas" :roll:, to which I responded, "it uses no gas, it's all electric." Then the light went on! I seems people need those key words to hear the message.