Simplest way to convert glucose into water and carbon dioxide other than burning?
I'd suggest you read into the Fenton process. Using an iron catalyst with hydrogen peroxide will break down (potentially) any organic matter into $\ce{CO2}$ and $\ce{H2O}$ within minutes or hours. The only drawback from your requirements is the pH, since I think this is only down in acidic solution, but you could do a little research to find out more.