Page 118 - Barbecue Chicken Made Easy

monitored the air temperature in the cavity above the can. A 16 ounce can extends several inches lower (below the chicken) than a 12 ounce can and is exposed to more heat so all three rose in temperature together and reached safe serving temperature at about the same time. The beer and space above the beer got hotter than the 12 ounce can, but still peaked at about 165°F, well below steaming. Some of the beer at the bottom of the can probably got hotter because it was exposed to hot air, but that liquid rises and mixes with the cooler beer above, so there is no way it will come close to the boiling point.
What about beer flavor? According to Scott Bruslind, Laboratory Manager at Analysis Laboratory, on average, 92% percent of beer is flavorless water and 5% is flavorless alcohol. All the flavor compounds are at most 3.5% of the weight: 1 to 2.5% sugars with 0.5 to 1% a mix of proteins, minerals, small chain organic acids, and esters, aldehydes, and ketones, which are a mix of acids and alcohols. Finally, 0.25% of the beer is carbon dioxide under pressure to make it bubble.
That means that in a 12 ounce can of beer, there is about 1 teaspoon of flavor, even in big dark beers like stout, the flavor compounds are a very small part of the brew. In other words, it is impossible for the beer to flavor the meat in any detectable way. Yes, you might be able to smell beer while it is cooking, but that smell is the result of immeasurably small parts per billion of the aromatics.
And no, it won't make any difference if you use soft drinks or other beverages. None of them will evaporate any faster or contribute any more flavor.
John Kass, a columnist for The Chicago Tribune, raves about beer can chicken. He says you need to put spices and herbs in the can.