Most places have potable water, so don't worry about drinking tap water. Bottled water is also available at low prices.
Refrescos are beverages made from fresh fruit cas, guanabana, sandia/watermelon, mora/blackberry, fresa/strawberry, granadilla/passion fruit, sugar and either water or milk. All sodas mom and pop diners serve these. You can also easily buy the standard international soda pops. 'Fresca', 'Canada Dry' and the local 'Fanta Kolita' fruit punch are recommended.
The national drink is called guaro, which is made from fermented sugar cane. It is similar to vodka, and is usually drunk with water and lemon. Note that it's not a very "clean" liquor, so exercise caution.
There are approximately 8 different national beers available and most international, which are sold in cans, bottles and even kegs. The most common beers in the country are Pilsen and Imperial: all bars and restaurants serve both. Bavaria, "Bavaria Negra" dark and Bavaria Light are considered higher quality but more expensive, Rock Ice and Rock Ice Limón lemon flavor has a higher alcohol percentage and is less common in rural areas. Heineken is locally made under license and is more expensive as well.
Ready-to-drink coffee is excellent and considered again to be among the best in the world.
