Detonation, basically, is a mixture of air and fuel with too little fuel. When it happens, it burns very hot. You get it by having too much air flow and not enough fuel and heavily advanced timing. What it comes down to is air/fuel mixture.

How do you fix it? Get a better fuel setup and tune it on a dyno.

Sugar in tank: You're screwed.
Water in tank: Runs like crap. Dump the tank, fill it up with gas, then disconncect the fuel line from the fuel rail and turn the ignition on several times to clean the water out.