High quality Tupperware can be a good option for storing dog food, as long as it's airtight and made from food-grade materials. However, many cheap Tupperware containers may not be airtight and this may lead to dog food unnoticeably spoiling and causing health problems. It is better to invest in a decent made-for-purpose high quality dog food container if you plan to store food for a long period of time (1 or more weeks). Make sure to clean Tupperware containers thoroughly before and after each use to prevent contamination, and ensure they are fully dry before storing pet food.