To speed up the growth of your eyebrows, you need to seal in moisture while you sleep. There are many products that can achieve these ends, some of which you probably already have at home. Some great options include:
Castor oil -- Castor oil contains proteins that encourage growth, but may irritate skin. Olive oil or Coconut oil -- Either of these oils seal in moisture to encourage growth. They are natural and inexpensive.
Petroleum jelly -- Petroleum jelly will help seal in moisture. Avoid using petroleum jelly if you have oily or acne-prone skin or you might break out.
Eyebrow growth serum -- Growth serums contain vitamins and peptides to encourage growth. These work very well, but it can cost anywhere from $20-80 per bottle.