In many areas of Colombia, it is common to have buñuelos (deep fried corn flour balls with cheese in the dough) and arepas (rather thick corn tortillas, often made with cheese and served with butter) with scrambled eggs for breakfast. Bogotá and the central region have its own breakfast delicacy of tamales - maize and chopped pork or chicken with vegetables and eggs, steamed in banana leaves, often served with home-made hot chocolate.
Empanadas, made with potato and meat with a pouch-like yellow exterior, are delicious and entirely different from their Mexican counterparts. Pastry is prevalent, both salty and sweet, including Pandebono, Pan de Yuca, Pastel Gloria, and Roscon. These vary in quality--ask the locals for the best niche places to indulge.
For lunch, especially on Sundays, you should try a sancocho de gallina (rich chicken soup, served with part of the chicken itself, rice and vegetables/salad). Sancocho is widespread throughout the country, with countless regional variants. On the coast it features fish, and is highly recommended. Another soup, served in Bogotá and the periphery, is Ajiaco (chicken soup made with three different kinds of potato, vegetables and herbs(guasca), served with rice, avocado, corn, milk cream and capers).
"Bandeja paisa" is common in most places, (the "paisas" are the natives from some departments in the North West, such as Antioquia, Caldas, Risaralda and Quindio). This includes rice, beans, fried plantain, arepa, fried egg, chorizo, chicharrón (pork crackling) with the meat still attached. It's a very fatty dish, but you can leave what you don't like, and if you're lucky enough, you could find a gourmet bandeja paisa in a good restaurant in Bogotá or Medellin. They are lighter and smaller.
There are a few chains throughout the country. In addition to worldwide franchises (McDonald's, Subway, T.G.I.F., which are specially focused on Bogotá and other big cities), Colombian chains are very strong and located in almost every city. Presto and especially El Corral serve outstanding burgers, Kokoriko makes broiled chicken and Frisby specializes in roasted chicken. Crêpes and Waffles, as the name indicates, is an upscale breakfast/brunch restaurant with spectacular... crêpes, waffles and ice cream. There are many international restaurants, including rodizios (Brazilian steak house style), paella houses, etc.
A great variety of tropical fruits can be tasted, and the corresponding variety in juices, from some of the oddest ones you can find around the globe (really) to the sweetest ones. You just must know how to find and prepare them. Anyway, anyone would be pleased to teach you. Some examples of those exotic fruits include: tamarinds, mangoes, guanabanas, lulo, mangostines (really great and rare even for Colombians), and a great variety in citrus. In addition, you can find some of those rich and strange flavors in prepared food like ice cream brands or restaurant juices. Most of Colombians drink juices at home and in restaurants, they are inexpensive and natural everywhere.
In Colombia there are a great variety of "tamales" if you like them, but be aware they are very different from their most famous Mexican cousins. They differ from region to region, but all of them are delicious. They are called "envuelto", the sweet tamale made of corn.
Regarding coffee, you can find a lot of products that are both made commercially and home-made from this very famous Colombian product, like wines, cookies, candies, milk-based desserts like "arequipe", ice-cream, etc.
Colombians are famous for having a sweet tooth, so you are going to find a lot of desserts and local candies like "bocadillo" made of guayaba (guava fruit), or the most famous milk-based "arequipe" (similar to its Argentinian cousin "dulce leche" or the french "confiteure du lait"). That just covers the basics, since every region in Colombia has its own fruits, local products, and therefore its own range of sweet products. If you are a lover of rare candies, you could get artisan-made candies in the little towns near Bogotá and Tunja.
Organic food is a current trend in big cities, but in little towns you can get fruits and veggies all very natural and fresh. Colombians aren't used to storing food for the winter, since there are no seasons in the traditional sense. So don't ask them for dried items like dried tomatos or fruits. All you have to do is go shopping at the little grocery stores nearby and pick up the freshest of the harvest of the month (almost everything is available and fresh all year). As for pickles and related preserved food, you can find them in supermarkets, but they are not common in family households.
Concerning potatoes, you must know the pre-Columbian civilizations had about 200 varieties of this plant. Well, Colombia as an Andean country, is not the exception. Even McDonalds recognized the quality of this product and buys them. But while you are there you don't want to go to McDonalds--you've got to try the local preparations like "salted potatos" (papas saladas) or "stewed potatos" (papas chorriadas).
All in all, in Colombia it can be fun to have the ingredients and the preparation of a lot of exotic recipes explained to you.
For breakfast, take a home-made hot chocolate. It is generally prepared with panela (dried cane juice), cinnamon and cloves, which gives it a special taste.
Colombia's national alcoholic beverage, Aguardiente tastes strongly of anise, and is typically bought by the bottle or half bottle. People usually drink it in shots. Each region has its own aguardiente, "Antioqueño" (from Antioquia), "Cristal" (from Caldas), "Quindiano" (from Quindio), "Blanco del Valle" (from Valle del Cauca) and "Nectar" (from Cundinamarca). There is also a variety of rum beverages, like "Ron Viejo Medellin" (also from Antioquia) and "Ron Viejo Caldas" (also from Caldas).
The water is drinkable right from the tap in most of the major cities, but be prepared to buy some bottles if you go to the countryside. Agua Manantial Bottled water is recommended, it comes from a natural spring near Bogotá. An advice make sure you do not use ice cubes, or drink any beverage that might contain non distilled water, ask if the beverage is made with tap or bottled/boiled water.
If you are lucky enough, and if you are staying in a familiar "finca cafetera" (coffee plantation) you can ask your Colombian friends not only for the selected coffee (quality export) but for the remaining coffee that the farmers leave to their own use. This is manually picked, washed, toasted in rustic brick stoves and manually ground. It has the most exquisite and rare flavor and aroma ever found.
Commercially you can find a lot of products made out of coffee too like wines, ice-creams, soda-pops and other beverages.