What foods are not a good source of carbohydrates?

Any foods that are mainly or only protein or fat such as meat, fish, eggs, oils, seafood and so on. They are not a good source of carbohydrate.
Good sources of carbs are grains (wheat, rice, oats, corn), starchy tubers (potato, yam...) or other vegetables, but everything that grows above ground has low carbohydrate content.
Sugar is a 100% carbohydrate, it raises blood sugar quickly, that's why diabetics take a piece of sugar if they have a dangerous slow blood sugar situation.