Strictly from the viewpoint of the anesthetic effects, patients can drink fluids and rapidly progress to full meals as soon as they feel up to it. This may be within an hour after a minor procedure. After major internal alterations, however, especially those involving the brain, the mouth, or the GI tract, the patient may need to wait much longer. Your surgeon or doctor will give you more detailed instructions about what you may eat or drink after surgery.
Anesthetists have moved away from the old practice of requiring day-surgery patients to drink and retain (i.e., not vomit) fluids prior to discharge. Studies have shown that pushing early fluid intake only promotes post-operative nausea and vomiting. It is far better to wait until the patient feels thirsty, and this need not delay discharge home.