If you want to replace lemon juice in cooking or medicinal applications, look no further than vinegar, lemon zest, orange juice, lime juice, white wine, vitamin C solution, or powdered citric acid. While these solutions should be used in different situations, all of them have some of the qualities of lemon juice and can act as an adequate replacement.
It is important to replace lemon juice in a recipe, of course, because it is both tart and sweet, providing a citrusy bite to many different dishes, a refreshing burst to cocktails, and a healthy boost to overall health. Lemon juice is rich in vitamin C, potassium, citric acid, B-family vitamins, calcium, manganese, iron, copper, and magnesium, making it an incredibly powerful ingredient in certain foods. Lemon juice is also common in alternative health remedies, as skin cleansers, tonics, hair washes, and infusions. It can help lower blood pressure, improve the immune system, build strong bones, prevent chronic disease, lower inflammation, optimize metabolism, promote healing, and detoxify the body. 
Serving Size : Nutrient Value Water [g] 92.31 Energy 22 Energy [kJ] 91 Protein [g] 0.35 Total lipid (fat) [g] 0.24 Ash [g] 0.21 Carbohydrate, by difference [g] 6.9 Fiber, total dietary [g] 0.3 Sugars, total including NLEA [g] 2.52 Sucrose [g] 0.43 Glucose (dextrose) [g] 0.99 Fructose [g] 1.1 Calcium, Ca [mg] 6 Iron, Fe [mg] 0.08 Magnesium, Mg [mg] 6 Phosphorus, P [mg] 8 Potassium, K [mg] 103 Sodium, Na [mg] 1 Zinc, Zn [mg] 0.05 Copper, Cu [mg] 0.02 Manganese, Mn [mg] 0.01 Selenium, Se [µg] 0.1 Vitamin C, total ascorbic acid [mg] 38.7 Thiamin [mg] 0.02 Riboflavin [mg] 0.02 Niacin [mg] 0.09 Pantothenic acid [mg] 0.13 Vitamin B-6 [mg] 0.05 Folate, total [µg] 20 Folate, food [µg] 20 Folate, DFE [µg] 20 Choline, total [mg] 5.1 Carotene, beta [µg] 1 Cryptoxanthin, beta [µg] 4 Vitamin A, IU [IU] 6 Lutein + zeaxanthin [µg] 15 Vitamin E (alpha-tocopherol) [mg] 0.15 Fatty acids, total saturated [g] 0.04 10:0 [g] 0.02 12:0 [g] 0 14:0 [g] 0 15:0 [g] 0 16:0 [g] 0.01 18:0 [g] 0 Fatty acids, total monounsaturated [g] 0.01 14:1 [g] 0 18:1 [g] 0 18:1 c [g] 0 Fatty acids, total polyunsaturated [g] 0.02 18:2 [g] 0.01 18:2 n-6 c,c [g] 0.01 18:3 [g] 0.01 18:3 n-3 c,c,c (ALA) [g] 0.01 Sources include : USDA 
Substitutes of Lemon Juice
Your reasons for needing to replace lemon juice may simply be a lack of lemons or possibly a lemon allergy that is putting you off the juice of this yellow, ellipsoidal fruit. Regardless of your reason, there are a number of alternatives that can deliver many of the same effects.
This is the most common and successful replacement for lemon juice, considering that limes and lemons are very closely related and have a somewhat similar flavor. Lemons tend to be slightly sweeter, but in the midst of a cocktail, it can be difficult to truly taste the difference. Lime juice is also rich in vitamin C and many of the same minerals, thus providing a similar health boost. However, if your reason for avoiding lemon juice is a sensitivity to citrus, try replacing the juice with another sweet juice, such as apple juice. For medicinal purposes, lime juice or another citrus juice is recommended as a substitution. 
Lemon juice isn’t always used for its particular flavor, but for the acid content that it contains. That particular acidity gives a certain flavor to many sauces and salsas. Therefore, other highly acidic fruits can often replace this juice in the cooking regard, as they all contain citric acid and can create that tartness in a dish. Orange juice is also similarly high in vitamin C, calcium and potassium, and can provide similar benefits. 
Another very good option for replacing lemon juice is white wine, due to the acidity present in the liquid. For the majority of dishes, particularly savory ones, a given amount of lemon juice can typically be replaced by half that amount of white wine. If you use an equal ratio, there will be too much acidity in the meal. Using white wine as a replacement for this juice is typically best in small amounts or else the taste will change drastically.
There is no sweetness in vinegar, but there is a decent level of acidity, making it an appropriate substitute when cooking savory dishes, as you aren’t necessarily looking for the sweetness, but rather the acidic bite. Vinegar should also be used in limited quantities to prevent it from overpowering the other flavors. Half as much vinegar (or less) should be used to replace a given amount of lemon juice. 
If you’ve used up all the juice from your lemons, but still need a bit more of its flavor, simply use the lemon zest that you have on the rinds of the lemons. It contains higher concentrations of many nutrients and releases the same smell and flavor when used in cocktails and other beverages. Lemon zest can even be purchased in dried form in most grocery stores. As mentioned, it has the same nutritional makeup as lemon juice, only in a more concentrated form.
Powdered Citric Acid
Acidity is required for canning, as well as when making jams and jellies. However, if you don’t have lemon juice on hand, citric acid is the most important component that you need. A very small amount of powdered citric acid, available at specialty health food stores, can be used to replace lemon juice. Powdered citric acid is about 10x more concentrated than lemon juice, so keep that in mind when using it in recipes. 
Vitamin C Solution
The high concentrations of vitamin C found in lemon juice are important to stop oxidation of certain foods and prevent them from going bad. If you need a lemon juice substitute for this purpose, simply mix up a vitamin C solution with a powdered form of this essential nutrient and use it on your other foods. This is also important if you rely on lemon juice for its immune-boosting powers. A diluted dram of vitamin C solution can also keep your body’s immune system in a great zone!