Will putting sugar in the gas tank of a car break eng?

Yes, putting sugar in a car's gas tank will very likely severely damage the engine. Sugar will dissolve in the gasoline to some extent, but it will also gum up the fuel injectors, fuel lines, and clog the fuel filter. This will starve the engine of fuel, causing it to misfire, run poorly, and eventually stall completely. The repair will likely be very expensive, possibly requiring the replacement of significant parts of the fuel system.