Brainteasers assess your creativity and your ability to ask the right questions. They are often very unstructured, making it difficult to practice them.

Example:

You have a five-liter jug and a three-liter jug. You need exactly four liters of water and you an unlimited source of water available. How do you do this?

Answer:
fill the three-liter jug with water and pour it into the five-liter jug. Repeat this process again. The five-liter jug only has two liters left in this second round, leaving exactly one liter in the three-liter jug. Empty the five-liter jug, and pour the remaining one liter in the five-liter jug. Now fill up the three-liter jug and pour into the five-liter jug - this gives you exactly four liters!