Bottled water is very common and is safe to drink; it comes con gas carbonated and sin gas non-carbonated. Water from the tap is unsafe to drink. Even Ecuadorians generally only drink bottled or boiled water.
Coffee is widely available in cafes and restaurants, and also sold in bean form. Tea is also common, usually with a good selection including herbal.
Fruit juice is plentiful and good, and you will often have many options: piña pineapple, mora blackberry, maracuyá passion fruit, naranja orange, sandía watermelon, naranjilla a jungle fruit, melon, taxo, guanabana, guava, etc. If you'd like it made with milk, sort of like a less-frozen milkshake, ask for a batida. Note that often juices are served lukewarm.
Aguardiente, often made from fermented sugar cane, is the local firewater. If possible, have some ground freshly into your cup from the sugar cane.