In some instances, it seems to mirror the use of Peace Water in being utilized for blessing and removing negativity. Other sources say its for victory and glory.
Judika Illes in her 5,000 Spells says the key ingredient is orange blossom water, and that "without it, it is no longer Glory Water." Much farther back, an informant of the folklorist Harry M. Hyatt gives a recipe for Glory Water: honey, brown sugar and balm mixed into rain water. He reports that genuine Glory Water only comes from Africa or Asia, and everything American made is but an imitation. He instructs it be rubbed on the body twice a day for 9 days, while reading a certain psalm from the Bible, in order to get one's wish. (Presumably one alters the psalm to match with one's wishes.)
The informant may have been right that it's an exotic mixture, but Agua de Gloria has its origins in hispanic ritual. It is made by soaking the petals of a native orchid in water to perfume it, and the resulting mixture is used in church processions. The recipe and history is given in the book Orchids of Mexico. Glory Water is scarcely mentioned in English language sources until fairly recently, but it goes back at least 100 years in Spanish-language sources. A 1917 article from the Journal of American Folklore indicates an even more simple recipe -- water blessed on the Sabbath with a Gloria recited over it.
Knowing it origins, it is probably best used as an all-purpose wish-granting water, similar to holy water.