Reuse tea leaves with the same method you used during the initial brew, pouring hot water over them and letting them brew for anywhere from one to 10 minutes, depending on the type of tea. However, you might need to leave the tea in the water for 30 seconds more than the initial brew to get as strong of an infusion.
Some types of tea rebrew better than others. For example, pu-ehr, which is a type of fermented black tea, is known for its ability to be reused up to 10 times with flavorful results. White tea leaves get sweeter with each additional use. Oolong teas have been known to develop different flavors with each brew. Herbal infusions, however, might not be as flavorful in subsequent uses as they were in the first.
Reuse tea leaves in the same sitting as their first use for the best results. If wet tea leaves sit overnight, they are prone to growing mold and bacteria that can produce undesirable flavors or make you sick. If you do save tea leaves to brew again another day, spread them out so they can dry instead of leaving them in a tight space.