One 100 g serving of mcdonald's, hot fudge sundae has 186 calories, 30.1 g of carbs, and 0.4 g of fiber.
Full macro and micronutrient breakdown, plus how this compares across diets, is on the McDONALD'S, Hot Fudge Sundae nutrition facts page.
Source: USDA FoodData Central - SR Legacy (2018-04)