Which theory about "doughboys" do you believe is right and why?

Question

1. The Baked Goods theory: doughboys were named such because of their method of cooking their rations. Meals were often doughy flour and rice concoctions either baked in the ashes of a camp fire or shaped around a bayonet and cooked over the flames.

2. The Button theory: U.S. infantrymen wore coats with unique, globular brass buttons. In one variation of this theory the buttons are said to reminiscent of the doughboy dumplings eaten by the soldiers and sailors of earlier days and which possibly had become part of American cuisine.

3. The Pipe Clay theory: During the 19th Century American enlisted men used a fine whitish clay called pipe clay to give "polish" to their uniforms and belts. It was a less than perfect appearance enhancer, however; in rainy weather the saturated clay came to look "doughie".

4.in marching over the parched terrain of the deserts of Northern Mexico the infantry stirred up so much dust that they took on the look of the abode buildings of the region -- hence

Answer 1

I heard it was because women volunteers would serve doughnuts and coffee to soldiers waiting for transport to the fighting.