Sugar-sweetened beverages are a major source of free sugars in Western diets. In response, several European countries have introduced taxes to encourage product reformulation and reduce consumption. This study assesses how these taxes affected sales in off-trade and on-trade markets, examines consumers’ potential substitution effects using Euromonitor data (2004–2019), and evaluates manufacturers’ reformulation responses through Mintel product-launch data (2010–2019). We focus on six countries that implemented such taxes, specifically Belgium, France, Hungary, Ireland, Portugal, and the United Kingdom, and additionally analyse Denmark, which introduced a similar tax earlier and repealed it in 2014, providing a reverse test case. Using a synthetic control approach, we construct counterfactual scenarios to estimate tax impacts. We find significant sales effects only under progressive tax designs, while reformulation emerged consistently, particularly where sugar thresholds and implementation timelines were clearly defined.