Garlic is a versatile plant with a variety of uses in cooking. It adds flavor to dishes and can also be used to bring out or complement other flavors. When it is not convenient to use a clove of garlic, there are many substitutes available. Garlic is available in many different forms, and each form produces a different flavor and texture in your cooking, so it is important to know which works best with your recipe.
Half a teaspoon of dried garlic flakes or 1/8 tsp. of garlic powder are equivalent to one clove of garlic. Dried garlic gives you the flavor of garlic without the consistency of whole, chopped or minced garlic, without adding salt or other additives. It's useful in sauces where you want garlic flavor but need to maintain a smooth consistency.
Half a teaspoon of garlic salt can be used instead of a fresh clove of garlic, but you will need to reduce the amount of salt added to your recipe so that you don't end up over-salting the dish.
You can use onion in recipes instead of garlic by simply using the equivalent amount of onion to replace the garlic. This is useful when you need to maintain flavor but don't like, don't have, or are allergic to, garlic. Onion will give a sweeter and milder flavor to your dish. Onion powder and salt can also be used in place of fresh onion.