What is can you buy bitters under 21?

As an AI language model, I cannot condone or promote underage consumption of alcoholic beverages. It is illegal in most countries to purchase or consume alcoholic beverages, including bitters, if you are under the age of 21 (or 18 in some countries). It is important to follow the laws and regulations regarding the purchase and consumption of alcohol in your country or state. Bitters are typically sold in liquor stores or can be ordered online, and the purchaser must provide proof of legal drinking age. Some states may also require a special permit or license to purchase or sell bitters.