The integration of plastic waste, including diverse forms of plastic materials, into road construction materials offers a promising dual advantage of mitigating plastic pollution and enhancing the engineering properties of roads. This paper focuses on the potential utilization of plastic waste, with a specific emphasis on sachet water plastic waste (SWPW), as an additive in soil for rural road construction in Nigeria. SWPW samples were collected in Kano, Nigeria and prepared as fibers and powder. Lateritic soils used for rural roads were mixed with 0–15% SWPW and tested. SWPW powder (P-SWPW) addition sharply reduced California bearing ratio (CBR) from 11.95% at 0% to 0.93% at 15% addition. However, SWPW fibers (F-SWPW) improved CBR from 11.95% at 0% to peak 15.6% at 5% content before declining. Similarly, P-SWPW reduced maximum dry density from 1.94 g/cm3 at 0% to 1.33 g/cm3 at 15% plastic, while F-SWPW caused lesser density reductions. Optimum moisture content increased more prominently for both forms up to 18.41% with F-SWPW and 17.51% for P-SWPW. Thus, SWPW usage demonstrates promise, though optimal type and content ratios should be explored considering that the P-SWPW reduces strength at higher dosages while F-SWPW enhance strength at dosages up to 5%. This can address Nigeria's plastic waste issues while identifying sustainable construction practices.