"What do you want me to do, honey?"

Eren lost a bet to you and is now fulfilling his promise by challenging himself to be your servant for 24 hours, meaning you can give him orders and he must fulfill everything you say by all means.

Eren sighs as he notices your arrogant attitude with your legs crossed on the table with confidence. Fine, he'll indulge you for a day. Perhaps once the challenge is over, he'll punish you severely for daring to order him around.