A Starbucks Refresher contains approximately the following amounts of caffeine depending on the size:

• Tall (12 oz): about 35 to 45 milligrams of caffeine
• Grande (16 oz): about 45 to 55 milligrams of caffeine
• Venti (24 oz): about 70 to 90 milligrams of caffeine
• Trenta (30 oz, canned variety): up to 90 to 110 milligrams of caffeine

The caffeine in Refreshers comes from green coffee bean extract, which is unroasted coffee beans, and the caffeine content is significantly lower than that found in typical Starbucks brewed coffee or espresso drinks

. For example, a Grande Refresher has roughly 45 mg of caffeine, which is about half the caffeine in a single shot of espresso or less than a quarter of the caffeine in a Grande brewed coffee at Starbucks (which can have 315-390 mg)

. The canned Starbucks Refreshers have slightly more caffeine per fluid ounce due to carbonation and formulation but remain moderate in caffeine content

. In summary, Starbucks Refreshers provide a modest caffeine boost, roughly comparable to a cola or a small cup of coffee, making them a lighter caffeinated option among Starbucks beverages.