The aim of the present study was to characterize selected by-products from Brazilian food industry and their in vitro digestibility. These by-products (cassava and orange bagasses and passion fruit peels) are potentially rich sources of dietary fibres, but currently they are mostly disposed. Their analysis revealed differences in composition for the same by-product type from different suppliers. Cassava bagasses were mainly composed of starch, with high variability among tested by-products (45–77.5% starch). In vitro experiments indicated that cassava bagasses had ~ 12% of resistant starch. The orange bagasses had free glucose and highly methyl esterified pectin as the main constituents (~23.5% of total pectin). Seventy-seven % of digestible glucose present in the orange bagasse were absorbed within 3 h experimental run. Passion fruit peels were a good source of fibres, especially pectin (~19%) and (hemi)cellulose (~16%). These in vitro experiments indicated that passion fruit peel had slower absorption of glucose than the other by-products, with 80% of digestible glucose absorbed within 5 h. In conclusion, the tested by-products are good sources of diverse types of fibres and have a great potential to be incorporated into different food products, decreasing food waste and contributing to a sustainable food system.