Is hanging fruit in front of juice shops until it rots, for the purpose of advertising, Islamically permissible, or is it considered extravagance and misuse of blessings?

If the purpose of hanging fruit is for advertising and attracting customers, then there is no harm in it, and it is not extravagance. A merchant spends a portion of his money to promote his goods. It is expected that he will remove and replace the fruit before it rots, and perhaps he will eat it or juice it before it spoils.