Traditional Malawian food revolves around one staple, maize, served in one form, nsima(n'SEE-ma). Nsima is basically a type of thick porridge, rolled into balls with your right hand and dipped into a variety of stews known as relishes. Those who can afford them eat relishes of beef, chicken or fish, but the many who can't make do with beans, tiny dried fish (usipa), pumpkin leaves (chibwabwa) and other vegetables. At breakfast, nsima can be served watered down into a soup, maybe with a little sugar. Local restaurants will serve nsima and relish for less than MK500 (US$3).
Food options in the major cities of Lilongwe and Blantyre are good. Fast food — to include burgers, pizza, and fried chicken — is very popular in Malawi. For sit-down meals, ethnic eateries (thanks to a significant ex-pat population) are popular. Do note that, in many restaurants, pork products are not served to accommodate the Muslim population.
Outside the larger cities, however, you might be a little underwhelmed with food options. Along the major roadways, you will find "tuck shops" featuring packaged cookies or Take Away Meals — meat pies or sausage rolls, for instance — which may or may not satisfy you.
Finally, in terms of hygiene outside the major cities, you are unlikely to find a proper washroom with running water. You will probably be given a bowl of water, a piece of soap, and a (damp) towel. Therefore, some travellers bring small bottles of anti-bacterial hand soap with them.
Tap water in major cities like Lilongwe, Blantyre, Zomba and Mzuzu is generally safe. Ask at the lodge/house you're at. Some travellers with weaker stomachs may be advised to avoid this drinking water. Bottled water is plentiful in all the major shops.
A traditional local drink worth trying is maheu, a somewhat gritty and vaguely yogurty but refreshing beverage made from maize meal. Factory-produced maheu is sweet, comes in plastic bottles and is available in a variety of flavours including banana, chocolate and orange, while home made versions are usually unflavored and less sweet.
The variety of soft drinks in Malawi is very popular - there's Coke, Sprite, Tonic, Ginger Ale, Soda Water, Cherry Plum, Cocopina and the very tasty, sugary Fanta's (coming in Orange, Grape, Exotic, Passion and Pineapple flavours). These are manufactured by SOBO, the glass bottles are on a deposit system. Expect to pay MK25 extra per bottle unless you bring some 'empties' with you.
The only beers you will generally find are brewed in Blantyre by Carlsberg, and its products are available in restaurants and stores throughout the country. A normal Carlsberg is known as a 'green', but the company also produces Special Brew, Stout, Classic, Elephant, Light and Kuche Kuche. You can also buy imported drinks such as Heineken, Kronenbourg, Smirnoff Ice, Bacardi Breezer and some ciders in certain bars. Malawi also produces its own spirits - notably Malawi Vodka, Malawi Gin, Malawi Rum, Gold Label Brandy and the cane spirit Powers. Malawi Gin & Tonic is a very nice, popular expat drink in the country.