Most acidic food liquids can be used to keep your apples (and other fruit) from turning brown.
Lemon and lime juice are well known. Vinegar is another that is often used.
If you plan to use your fruit in a mixed (vegetable and fruit) salad, you can also use some salad dressings.
You do not need pure lemon or lime juice or vinegar. Diluted with water or juices of other fruits works. Many fruit juices themselves will do the job, if enough of them are used.
And it is not just the fruit, vegetables can go brown as well and the same liquids will mostly be good for that as well.
There are also chemicals which are food safe (often made from food items) which will do the work, some are liquid, some are powders which can be sprinkled over the fruit.
The best known is citric acid, but there are many antioxidants, this 'e-number list' lists many that are food safe, not all on the list will be suitable.