None of the services you mention, App Services, Azure SQL or Azure Storage, support the ability to stop them and avoid charges. All of these are PaaS services that charge for the time the exist. A couple of things to think about:
- Azure Storage only bills for content, so if you have nothing stored you won't pay anything
- Azure SQL does have a serverless option, where you only pay when it is used. It has a number of limitations so be aware of these, but it may help - https://learn.microsoft.com/en-us/azure/sql-database/sql-database-serverless