Birkenstocks will last a long time if you take good care of them. Don't throw them in the washing machine or soak them in water. Most Birkenstocks are made of several different types of materials. There are different cleaning instructions for each material. Using products to maintain the nubuck and cork will also help extend the life of your shoes.
Brush nubuck or suede with a suede brush to remove dirt. Remove any stains from the nubuck or suede with a mild leather cleaner. Then brush again after the cleaner dries.
Clean smooth leather with a mild leather cleaner. Shine with regular shoe polish.
Wipe Birko-Flor and Birkibuc with a damp cloth. Remove stains with a mild leather cleaner or soap and water.
Wash EVA Malibu and Waikiki sandals with mild soap and water. Dry away from direct sunlight.
Regularly apply a spray-on water repellent to nubuck and suede. Apply Birkenstock's "Cork Life" whenever the cork loses its shine.
Don't immerse your Birkenstocks in water (except for the EVA Malibu and Waikiki models, which are waterproof and washable). Too much water is bad for the leather, the glue and the sealants. Rinse buckles if they have been exposed to salt water.