Please suggest what foods or drinks to avoid with an overactive thyroid?

Avoid stimulants: If your thyroid is overactive, your metabolic rate will be higher, and you will need more calories, fluids, etc. Usually appetite/thirst drives this. But you are already hyper...Stimulated by the thyroid hormone. Careful with the caffeine, and by all means don't use extra stimulants, like red bull, or equivalent. See your doctor and get your thyroid under control.

Watch OTC meds: Agree w/ dr kern's answer. I would also suggest caution with otc (over-the-counter) products, especially those containing a decongestant used for relief of cold and allergy symptoms. Many otc products include a warning not to use them if you have thyroid disease. If your overactive thyroid is mild or has been successfully treated, they may be fine, but check w/ your doctor.