The beverage comprises carbonated water, sugar, citric acid (acid), natural flavourings including quinine, and sweetener (sodium saccharin). These ingredients combine to deliver the signature taste of Schweppes Tonic Water, balancing sweetness with the characteristic bitterness of quinine.​

Schweppes Tonic Water 150ml is free from the 14 major allergens, including gluten, dairy, nuts, soy, and sulphites, making it suitable for individuals with common food allergies. It is also gluten-free, GMO-free, and suitable for vegetarians and vegans. However, it contains sodium saccharin, an artificial sweetener, which may be unsuitable for individuals with sensitivity to such additives. Consumers are advised to check the product label for the most accurate and up-to-date information.