Liquid glucose, sometimes called glucose syrup, is a liquid sweetener used to keep icings and baked goods moist and soft. A number of other liquid sweeteners can be used in a 1-to-1 replacement if you don't have liquid glucose, although the end product may taste somewhat different depending on which sweetener you use.
Corn syrup is probably one of the best replacements for glucose syrup. It's actually a form of glucose syrup, which can be made from any number of starchy foods, including corn, potatoes or wheat. In the United States, corn syrup is one of the most readily available types of glucose syrup. Light corn syrup is a better replacement than dark corn syrup because the flavor isn't as strong. It has 62 calories and about 17 grams of sugar per tablespoon.
Golden syrup is a liquid sweetener more commonly used in the United Kingdom and the Caribbean than in the United States. It's a little thicker and darker in color than glucose or corn syrup and has a stronger flavor, but still makes a good substitute. It's also called cane syrup, cane juice and light treacle. Each tablespoon has 56 calories and about 15 grams of sugar.
A Homemade Alternative
If you don't have glucose syrup or corn syrup available, you can make a substitute at home. One option is cane sugar syrup, made by mixing granulated cane sugar with water and a small amount of cream of tartar and salt. Cane syrup has about 56 calories and 15 grams of sugar per tablespoon.
Another option is to make simple syrup, which is a mix of two parts sugar and one part water heated until the sugar is totally dissolved in the water.
Other liquid sweeteners can also be used with varying results. Honey is sweeter than corn syrup and glucose syrup, and molasses has a stronger flavor, but they are closer in consistency than maple syrup, which is thinner and not as good of a substitute. Molasses has 58 calories per tablespoon and about 15 grams of sugar, and honey has 64 calories per tablespoon and about 17 grams of sugar per tablespoon.