You have to rule out that the supply is a composite supply. A supply can be a mixed supply only if it is not a composite supply.
If the items can be sold separately, i.e., the supplies not naturally bundled in the ordinary course of business, then it would be a mixed supply.
If a person buys canned foods, sweets, chocolates, cakes, dry fruits, aerated drink and fruit juices separately and not as a Diwali gift box, then it is not considered a mixed supply. All items will be taxed separately