The variation on the spirits in the fuel tanks story I have heard is a USMC (or Navy) A-4 squadron on detachment to Guantanamo Bay. The centreline tank on one of the Scooters was steam cleaned and then filled to the brim with Cuban rum which, I understand, can be bought for peanuts and was paid for by a whip round amongst the squadron pilots. The cap on the tank was locked in place (sorry, don't know the technical terms).
On the flight back the A-4 carrying the rum had to divert into another airfield to take on more fuel as, of course, it wasn't carrying as much avtur as the rest of them. The pilot signed in, grabbed a coffee and returned to the line just as his trusty steed had completed being refuelled. The bowser driver turned to the pilot and said in a cheerful tone:
"Don't know why the centreline tank was locked, sir, but I managed to squeeze a bit more into it for you."