In this case, you can thank your elder sister in the following ways:

1. It's very kind of you to bring so much food. Thank you very much. Express your gratitude simply and directly.

2. Elder sister, you are spoiling me and bringing so many delicious foods. I really don't know how to thank you. While expressing gratitude, I also expressed my sister's kindness and made myself feel flattered.

3. It's so sweet, elder sister. I'm so happy to see what you brought, and I appreciate your kindness. I'm glad to see the food my sister brought, and I'm grateful for her kindness.

4. Elder sister, I accept your kindness. I am deeply moved by such delicious and rich food. I was moved by expressing my sister-in-law's behavior directly, and expressed my confiscation and cherish for her heart.

5. My good elder sister, you have brought such healthy and delicious food, and I'm going to be a foodie. Your kindness really warms me up. Express your love for eating in an exaggerated way, and at the same time convey that your sister's actions make you feel warm.

6. Elder sister, thank you for your concern and care. Such a rich food makes my mouth water. You really know my appetite. Expressing my sister's behavior makes me want to eat, which shows that my sister knows her taste very well and expresses her gratitude for her concern and care.

All the above are intimate, touching and vivid expressions. It not only conveyed his own joy and emotion, but also expressed his gratitude for his kindness, and also showed the close relationship between the two sides. My sister-in-law will also feel that her intentions have been understood and cherished, which is very gratifying. This is a more tactful and sincere way to express gratitude.