Objective: To compare the sugar content of items at four multinational fast-food chains, across three countries. Design: Total sugar (g)/per serving was extracted from online nutrition information, and sugar/100 g serving was calculated. Foods were categorised as: breakfast sandwiches, burgers, sandwiches, desserts and condiments. Beverages were categorised as fountain, frozen or pre-packaged. Sugar (g) was compared across countries using linear mixed-effects models. Pairwise comparisons were performed with Tukey–Kramer adjustments. Setting: USA, Germany and Australia. Participants: Burger King™ (Hungry Jack’s™), Kentucky Fried Chicken™, McDonald’s™ and Subway™. Results: Differences in total sugar/100 g or ml were observed across countries for burgers (n 104), desserts (n 110), sandwiches (n 178), pre-packaged beverages (n 36) and frozen beverages (n 72). Comparing identical items across countries (e.g. BigMacTM from McDonalds in USA, Germany and Australia), burgers (n 10 available in all three countries) had lower sugar content in Australia (3·4 g/100 g) compared with the USA (4·7 g/100 g, P = 0·02) or Germany (4·6 g/100 g, P = 0·04), yet no differences were observed in other food categories. Comparing the same beverages across countries (e.g. chocolate shake from Burger King), frozen beverages (n 4 available in all three countries) had lower sugar content in Australia (14·2 g/100 ml), compared with the USA (20·3 g/100 ml, P = 0·0005) or Germany (17·8 g/100 ml, P = 0·0148), yet no differences were observed in other beverage categories. Conclusions: Heterogeneity in fast-food sugar content across countries suggests that reductions are possible and should be implemented to reduce health risks associated with excess added sugar intake.