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The sugar content of Solanum lycopersicum (tomato) fruit is a primary determinant of taste and quality. Cultivated tomato fruit are characterized by near‐equimolar levels of the hexoses glucose and fructose, derived from the hydrolysis of translocated sucrose. As fructose is perceived as approximately twice as sweet as glucose, increasing its concentration at the expense of glucose can improve tomato fruit taste. Introgressions of the Fgr^H allele from the wild species Solanum habrochaites (LA1777) into cultivated tomato increased the fructose‐to‐glucose ratio of the ripe fruit by reducing glucose levels and concomitantly increasing fructose levels. In order to identify the function of the Fgr gene, we combined a fine‐mapping strategy with RNAseq differential expression analysis of near‐isogenic tomato lines. The results indicated that a SWEET protein was strongly upregulated in the lines with a high fructose‐to …