Personally i don't do energy drinks thing (i'm a rare case i guess! >.<), but yeah, I do understand and respect what you've mentioned and it's absolutely fine. Maybe instead of holding it down to shoot you could have sort of a temporary weapon boost that gets on cooldown after use?
Some games do have a normal skill if you tap, and if instead you hold on for a bit longer the key, it activates something different. That kind of thing.
I hope this helps, cheers and thank you for the reply :)