What is the difference between hasty generalization and sweeping generalization?

They are essentially the inverse of each other. A sweeping generalization is applying a general rule to a specific instance (without proper evidence), and a hasty generalization is applying a specific rule to a general situation (without proper evidence). For example:

You get what you pay for. Therefore, it is better to spend $200 on that t-shirt at that boutique shop than buy the same one at Marshall's for $29.

This is an example of the sweeping generalization. Generally "you get what you pay for" might be a good rule, but it certainly does not apply to all situations, and attempting to make it fit to all situations without proper consideration (or evidence) is fallacious.

That $29 shirt at Marshall's is a great deal, therefore, everything at Marshall's is a great deal.

In this one instance, the $29 shirt that we know goes for $200 in the department stores is a great deal. However, to conclude that because of this, everything that Marshall's sells is a great deal, is an example of the hasty generalization fallacy. In fact, this is what marketers do. They have what is called a "loss leader" where they lose money on a product or service just to bring people in and get them to commit this fallacy, ultimately spending a lot more on their overpriced items.