Kelkin Vitamin C Effervescent 1,000mg Tablets (20). Vitamin C has a number of important roles within the body, it can contribute to the normal functioning of your immune system while also contributing to the reduction of tiredness and fatigue.. Ingredients. Citric Acid, Acidity Regulator: Sodium Bicarbonate, Ascorbic Acid, Maltodextrin, Flavouring, Sweeteners: Sodium Saccharin & Sorbitol, Colours: Beta Carotene & Red Beet