Spanish classes test this constantly, and it is one of the tidiest lists in geography: 20 countries, 20 capitals.
Play the Spanish-Speaking Countries Capitals Quiz.
The full list
Europe: Spain — Madrid.
North & Central America: Mexico — Mexico City · Guatemala — Guatemala City · Honduras — Tegucigalpa · El Salvador — San Salvador · Nicaragua — Managua · Costa Rica — San José · Panama — Panama City.
Caribbean: Cuba — Havana · Dominican Republic — Santo Domingo · Puerto Rico — San Juan (a US territory, often included in class lists).
South America: Colombia — Bogotá · Venezuela — Caracas · Ecuador — Quito · Peru — Lima · Bolivia — La Paz and Sucre · Chile — Santiago · Argentina — Buenos Aires · Uruguay — Montevideo · Paraguay — Asunción.
Africa: Equatorial Guinea — Malabo. This is the one almost everyone forgets, and the one teachers love to ask.
The easy pattern
Five capitals share their country's name or a near version: Guatemala City, Panama City, Mexico City, plus San Salvador for El Salvador. That is four answers for almost no effort.
The hard four
Tegucigalpa, Asunción, Malabo and Sucre. Drill just these in isolation — everything else in the list is either famous or self-naming.
Study tools
Use the flashcard generator for printable cards, the country comparison tool to see two Spanish-speaking countries side by side, and the study planner to spread the 20 over a week.