Glace fruit can be a great ingredient in fruit cakes and other items, but they can be tough to work with and can be way too sweet in an item.
The solution to both problems is the same, rinse the fruit before adding it. When I make English fruit cake, my recipe calls for both candied citrus peel and glacee cherries, which I rinse until the water runs clean. The cherries in the recipe are cut in 4, and since the pit is removed, there is a cavity which can hold the syrup even after a thorough rinse before chopping, I also rinse them after chopping to get them really clean.