Back in the 50's and 60's this was a ploy by strikers at our local textile mills!!! They would put sugar in gas tanks of management folks and "scabs"!!!
It will ruin your fuel system and engine if it gets that far. If you ever fooled with a 2-cycle outboard motor that has sat up for several years you get the equivalent of varnish from old gas mixed with
oil.....Sugar accomplishes the same thing but much faster!!!
If you suspect sugar in the gas, drain and clean the entire system ASAP and DO NOT RUN THE ENGINE!!
As for solubility of sugar in gas.....It may not be very soluble but it won't take but a few PPM to do the damage. That is to say as little as a teaspoon full will do the job!!!
Good Luck,
Jack