Preparation varies with the food type. Some foods can be eaten in their natural form, such as brownies and fruit. Other foods require adding water, such as macaroni and cheese or spaghetti. Of course, an oven is provided in the space shuttle and the space station to heat foods to the proper temperature. There are no refrigerators in space, so space food must be stored and prepared properly to avoid spoilage, especially on longer missions.
Astronauts brush their teeth just like they do on Earth. There is no shower on the orbiter, so astronauts must make do with sponge baths until they return home. Each Space Shuttle has a toilet that can be used by both men and women. Designed to be as much as possible like those on Earth, the units use flowing air instead of water to move waste through the system. Solid wastes are compressed and stored onboard, and then removed after landing. Wastewater is vented to space, although future systems may recycle it, such as they do on the International Space Station. The air is filtered to remove odor and bacteria and then returned to the cabin.
Top 10 Cool Facts about Space -
http://listverse.com/science/top-10-cool-facts-about-space
