Saute the onions in oil till translucent...and lightly browned. As the onions begin to brown, add all other ingredients and stir for 30 minutes. Let mixture cool to room temperature and place small batches in a food processor or blender and puree till smooth. Put mixture back into a large covered pan and simmer slowly for approximately 2 hours. Sauce can be refrigerated or frozen for future use. Use your imagination for the selection of the soda....and of course any other ingredients! I prefer using this as a "dippin" sauce....but I am a professional "dip"!