Feeding sugar syrup to honey bees is often a primary beekeeper task. In the spring of the year, diluted syrup (40% sugar/60% water by weight) can be fed to increase brood rearing. In other times, when bees are low on stores, a more concentrated solution, up to 60% sugar reduces the need for the bees to evaporate excess moisture. Thus, feeding can either be stimulation to promote growth or survival for colonies
Another thing that can be varied in feeding sugar is the time it takes a colony to consume a given quantity of syrup. This can be metered by the beekeeper by changing the number and size of holes in the feeding apparatus. In an emergency bees can be fed granulated sugar placed on the top bar. A similar technique can be something called a “candy board,” often used in cold weather.
The advent of high fructose corn syrup (HFCS) in the 1970s helped the beekeeper’s sugar feeding program. It was cheaper than sugar, or so it appeared at first glance. However, to get equivalency in price with sugar, only the solid content of HFCS should be considered in the pricing. An advantage of corn syrup is that it was already liquid. This avoided labor costs of mixing dry sugar with water.
A number of examples for feeding honey bees sugar is found on youtube.com. Be careful using anything recommended that is not part of standard ingredients: crystallized cane sugar and water. Adulterants like salt, essential oils, etc. are generally not recommended, although some beekeepers report success with these substances.
Most beekeepers feed sugar syrup in a closed system, which ensures the colony being fed gets the nutrition. However, another possibility is what is called “open feeding.” Basically a food source is provided at a single site within an apiary and all colonies are allowed to access it. This has several potential downsides; more populous colonies will get most of the food, out competing weaker ones, often the targets of feeding in the first place. It may also lead to spreading of diseases and/or robbing.