"Eating lots of delicious greasy food always makes me sleepy," he said, as though it were the most obvious answer.
This was entirely true, but still, it wouldn't do very well to fall asleep in a restaurant seat. The waitress returned with their bill, which woke Orsino up quite well as he took it and skimmed it. He held it up and waved it in front of Penny.
"You paid last time, so I'm thinking it's my turn."