It is best to assume that you will have difficulty finding daily essential items in Cuba. Although the larger, more modern hotels are well-equipped by Cuban standards, it is wise to pack a towel and washcloth for travel away from the bigger cities. There are no coin laundries in Cuba, and most hotels offer a laundry service that charges on a per piece basis. Given this, it is useful to pack a sink plug and travel packets of detergent. Particularly along the coastal areas, mosquitoes and sandflies are a problem and insect repellent is recommended.
Sanitary standards are very high in Cuba, and the drinking water is safe in most places.
However, if you are going off the beaten track, bring a supply of antibiotic cream, antiseptic swabs or lotion, water-purification tablets, Imodium or Lomotil for stomach upsets, and other basic health items. In a country of chronic shortages and scarcity, little gestures and things are much appreciated. Those little soaps and shampoos Americans collect at every hotel and motel they stay at will be welcomed by any Cuban. Used and clean clothes and shoes will likewise find a second life in Cuba. Whatever half-used items are still in your bag at the end of your visit to Cuba, consider leaving it all behind for a Cuban.