In the western dessert we were trained that in the event of running out of petrol, the proper procedure was to.
1= Open your small pack.
2= remove the cork from your water bottle an cut it into four pieces.
3= replace your spark plugs with the cork segments.
4= select four needles from your Hussif. ( Also known as Housewife ), and insert said needles into cork segments.
5= Remove bar of soap from wash-kit and stuff soap into float chamber.
6= fill petrol tank with hot water.
7= crank starting handle vigerously, ( What's a starting handle grandad "?
This causes the soap and water to mix, thus creating bubbles, the bubbles travel along the fuel lines and enter the cylinders. Bubbles being bubbles they tend to rise and so impinge upon the needles, thus bursting and driving down the pistons.
N.B. Care must be taken upon returning to the motor pool to inform the Vehicle Mecs. So that the system can be flushed and re-converted to petrol.