おごる (ゆうしょくを~)
おごる (ゆうしょくを~) · ogoru (yuushokuwo~) · JLPT N1 · noun
dainty
🍽️ 奢る = 奢 (luxury) + る: splurge your money on someone, like paying for their dinner
The kanji 奢 means luxury or extravagance. When you treat someone, you spend lavishly on them, so おごる fits. Use を for the item: ゆうしょくをおごる.