Determining the sugar content of liqueur is not an easy task. Hydrometers and refractometors do not give anywhere close to accurate results when water, alcohol, and sugar and present in a mixture. DO NOT TRUST or believe any advise that says you can determine the alcohol OR the sugar content of any liquid that contains water, sugar, and alcohol with a hydrometer OR a refractometer..... IT CAN'T BE DONE !!! Here is my method: Place about a half pint to a pint of the liqueur your are trying to analyze in a double boiler with a fairly tight fitting lid that has a hole in it in which to put a thermometer. The thermometer should NOT touch the bottom of the pot, but should be suspended in the liquid. This is a redneck version of the sophisticated lab equipment that commercial concerns use.... Put the double boiler (obviously with some water in the bottom pot... duh) on a burner on low to med-low heat. Watch the temp gauge CAREFULLY! Note that alcohol will boil away starting at 168 degrees F. and continue to boil off until about 190 degrees F. This covers the complete spectrum of alcohols, from the most UNDESIRABLE at the low end to the most UNDESIRABLE ones at the high end. But if your pot contains a commercial liqueur then you should not have to worry about the undesirables..... they will have been long gone. So, watching the thermometer keep the temperature as close to 180 as you can.... adjusting the heat up or down, until there is NO MORE STEAM or evidence of evaporation coming from the liquid. This will take from 30 minutes to an hour, or even longer. The best way to tell if the evaporation is done is to suspend some kind of glass or plastic cover over the double boiler. DO NOT let the temp exceed 180 degrees F. When the evaporation is ended, all the alcohol has been eliminated from the liquid leaving only water and sugar. Now you can accurately use a hydrometer (specific gravity, i.e. potential alcohol ABV) or a refractometer (measurement of brix) to determine the exact sugar content of the original liquid.