about 1.8x10^24 sugar molecules.
Since we have 1 liter of a 3 Molar solution of sugar, we have 3 moles of sugar molecules. To convert from moles to molecules, just multiply by Avogadro's number which is 6.0221409x10^23. So
3 * 6.0221409x10^23 = 1.80664227x10^24
Rounding to 2 significant figures gives 1.8x10^24 molecules.
