Oxygen needs to be taken in through the lungs. I doubt people could efficiently "breathe" through their stomachs.

Wouldn't inhaling soda cause you to drown?

Wouldn't the oxygen react with the soda in a high pressure environment?

I'm not sure about the pressure. I know that regular soda works there.

As for not absorbing oxygen - at high altitudes, I'm not thinking this will save anyone's life in terms of what an oxygen tank/mask would do, it would only temporarily increase the oxygenation levels of the blood. I'm assuming that some levels of oxygen would in fact be absorbed through the stomach lining, and breathing in over the opened bottle would provide higher oxygenated air.

To drowning - I would imagine that one would only drown if you have to breath in the water. Drinking it down wouldn't necessitate liquid entering your lungs (though at high altitudes, this does happen).

I wonder why I've never heard anyone propose eliminating carbonated beverages to reduce CO2 expelled to our atmosphere?

Yes, it's silly, but I'm really don't believe that our CO2 production for energy can be curtailed (unless/until humans start to die) and ironically, this small amount expelled by drinking soda could actually be ended at any time.

Carbonated drinks exist because carbon dioxide has the unusual property of being more soluble in cold liquids. Replacing this with oxygen may not achieve the same effect, though oxygen too is water-soluble. Primarily, oxygen is highly reactive in solution. Finding a tasty drink that factors in possible oxidization would be a tricky task, as oxidization is often what spoils many foods.

this idea FAILS

utterly FAILS, for so many reasons-you cant absorb the oxygen through your stomache-the oxygen would oxidize the sugar changing the flavor-the oxygen would allow bacterial growth in the soda-oxygen will not react in liquid the way that co2 does, co2 allows massive amounts to be dissolved, and will seperate with minor pressure changes, o2 doesnt!

As for reducing the amount of co2 in the atmosphere, I think that co2 sources are plentiful, such that the soda companies do not have to create co2 for the soda, so if they aren't using it from whatever source that source may simply vent to the atmosphere. Think of, say, mushroom farmers drawing off and concentrating the co2 created by their mushrooms and selling that co2 to the soda companies. If there was no market for it, the farmers would likely just vent the co2 to the outside air.