Restorative things give you energy or make you feel better. Your dad might have a favorite restorative chicken soup he makes you whenever you have a cold.
Antibiotics can be restorative to a patient with an infection, and a good night's sleep is almost always restorative, no matter how tired you are. If something brings you back to life or helps you recover, it's restorative. Sometimes people use this word as a noun, to mean "medicine for strength." Restorative has a Latin root, restaurare, "repair, rebuild, or renew."