Isn't it true when we enjoy a lazy Sunday brunch or an elaborate meal with family or friends we like to top up the fun with a siesta? So it is more to do with the quantity of food that makes us feel drowsy rather than the type of food I believe.
We all Indian are tempted to enjoy tasty dishes and Sambar - rice too included in this class. We may over consume them sometimes resulting in over sleepy.
'Idhuvum Kadandhu Pogum "
Even this challenging situation would ease