Vientiane has the best and most varied food scene in Laos, mixing Lao, French, Vietnamese, and international cuisines.
The riverside along the Mekong fills with food stalls in the evening, serving grilled meats, papaya salad, and sticky rice at low prices. This is the best place for cheap, authentic Lao street food.
The Scandinavian Bakery on the main square (Nam Phu) is a Vientiane institution. Good European pastries, coffee, and light lunches. A pleasant spot to recharge after temple-hopping.
French restaurants and bakeries are scattered through the old quarter, a legacy of the colonial era. Fresh baguette sandwiches are sold from carts on nearly every street and make for an excellent cheap breakfast.
For Lao food, look for the small local restaurants along the side streets near the Mekong. Noodle soup (pho or khao piak sen) shops open early for breakfast. The Lao beer gardens that open in the evening are great for grilled chicken, laap, and Beer Lao on the riverside.