Like what? Alcohol isn't flammable unless it's over 63%, and you aren't allowed to bring duty free alcohol on the plane.
Alcohol is flammable around 40%. French cooks aren’t using overproof brandy to do flambé.
Gunpowder doused in alcohol is, very famously for people interested in the history of rum, flammable if the alcohol is around 57.1% or higher, but straight alcohol/water without gunpowder is flammable at a lower strength than that.
Duty-free purchases are all hand carried into the aircraft, and "tamper-proof" bags are nothing of the sort.