Coffee is often compared in terms of sweetness and is common to see tasters describe a brew as “sweet” during Cupping, but coffee has no sugars and it’s not fully understood what exactly we are describing as sweet.
Coffee beans do contain sucrose, but the roasting process degrades about 97% of it. The amount of sucrose that ends up in the brew is so low that it’s below the sensory threshold concentration, meaning it is impossible for us to perceive it.
There are some carbohydrates (arabinogalactans) that can also be perceived sweet and are usually present in the brew in high enough concentrations, but their influence in the brew sweetness is still an hypothesis. It’s also possible that the sweet flavor actually comes from sweet aromas instead of detected by our taste buds.