There are a few things you can do to clean inside of boots if they have been stored in a dirty or wet environment. First, you can use a mild soap and water to clean the inside of the boots. Second, you can use a vacuum cleaner to suck up any dirt and debris that has built up on the inside of the boots. Finally, you can use a dryer to heat up the dirt and debris until it liquefies and is able to be cleaned away.