From Kosice train to Budapest-Keleti, train to Pecs, train to Pecs-Külvaros, then line 638 bus to Osijek. 12hrs 06min 37€. From Košice bus to Clark Ádám tér, bus to Budapest, line 1131 bus to Mohacs, then line 638 bus to Osijek. 12hrs 33min 121€. From Košice drive to Osijek. 6hrs 10min 81€.