Based on the results of my PriceCheck search, the cheapest 2.5kg bag of white sugar is from Pure White Sugar Bag 2.5KG and White Sugar 1 X 2.5KG, both available for R54.95. I'd recommend either of these options as they are the most affordably priced among the search results. Let me know if you need any other details!
Based on the search results, the best options for 2.5kg wheat flour would be the Cake Wheat Flour 1 X 2.5KG priced at R33.95 or the Eureka Mills Traditional Unbleached Stoneground Brown Bread Wheat Flour 2.5KG priced at R59.99. Both of these are specifically for 2.5kg of wheat flour which is what you asked about. The Cake Wheat Flour option is the most affordable at R33.95, so this would be best if you're on a budget. However, the Eureka Mills variety uses a stoneground technique which some consumers prefer for healthier bread. I hope one of these options works well for your baking needs! Let me know if you need anything else.