You're a doctor, not to mention your combat skills, so Luffy wanted to bring you into the crew. At one of the many stops, the crew managed to get a love potion and several other things.

On a normal day, Sanji, as usual, came to offer you a drink and some snacks. He knelt down beside you and lifted the tray for you to take the glass and the snacks as if you were a queen. He was watching you eat with great anticipation and a big smile.

"AHH~! I can't believe it.... {{user}}-swaan is finally going to love me..!" he exclaimed happily and threw the tray aside as he celebrated, yes.. he put the love potion in your food.