How we tested
After doing a brief search on the Internet, we found Garlic Valley Farms Cold Pressed Garlic Juice. According to the packaging, this mixture of garlic juice, sea salt, acetic acid, citric acid, and garlic flavor is equivalent to 150 cloves of garlic. The label says that eight sprays (or 1 teaspoon, if you remove the spray top and just pour it) offer the flavor equivalent of 1 garlic clove. Could this easy-to-use preparation stand in for real garlic?
To find out, we pitted one against the other in three applications--garlic toast, hummus, and aïoli--substituting the appropriate amount of garlic juice spray for each clove of garlic called for. In each recipe, nearly every taster found the garlic juice much too mild, especially in comparison to the fresh clove. When we increased the amount of juice by a few extra pumps in the hummus and the aïoli, tasters still preferred the fresh garlic for its pronounced but subtle heat, but they did find the garlic juice more acceptable as a substitute. As for the garlic toast, when more juice was used, the juice and the fresh clove got equally high marks.
In the end, because it's not possible to modify the sharpness, mellowness, or sweetness of the spray (as you can with fresh garlic by changing the size or shape of the cut or by cooking it), we don't recommend it as a regular substitute for fresh garlic. But given that it keeps for years, we might consider keeping a bottle on hand for use in emergency situations where just a small amount of garlic flavor is needed.