The answer to this question depends on the type of hibiscus plant you have. For instance, if you have a Hibiscus rosa-sinensis, vinegar is an effective way to kill spider mites and other pests.
Hibiscus plants are very susceptible to pest infestation. They need a lot of water and nutrients which they absorb from the soil. So it is important to maintain their health by keeping them free of pests and rot, which is sometimes caused by overwatering or too much fertilizer.
Vinegar has been used for years as a home remedy for cleaning plants because it has antifungal properties that help prevent fungal growth on surfaces like leaves and stems of the hibiscus plant.