One of the signs of a true friend is that they not only like you and care for you but they also honor and like the ones you cherish/love, such as your family. Likewise, If you really love Allah, then you would try your best to show your love at all times to His beloved Messenger Muhammad (SallAllahu 'alaihi wa sallam) by regularly following his Sunnah/tradition, for the sake of Allah.
Allah knows best. It is a Sunnah to always pray for the host, as their Muslim guest, or for the one who feeds you for Allah's sake. So when someone offers you something to eat or drink and gives you food or some drinks, even a glass of water, it is good manners to pray for them, saying:
"Allahumma At'em man at'amany wasqi man saqaani. Ameen."
Its English meaning:
"O' Allah, give food to the one who gave me food, and give drink to the one who gave me drink. Amen."
There are a few occasions when a host serves you food in a way that you may think is 'extravagant' or 'too much', that sometimes you feel so obliged to return their extreme generosity and favors. To do that you can insha-Allah say a sincere du'a for them:
"Allahumma baarik lahum feema razaqtahum, waghfur lahum warhamhum. Ameen."
Its English meaning:
"O' Allah, bless them in what You (Allah) have provided for them, and forgive them and have mercy on them. Amen."
Saying the above du'a/supplications is very much similar to praying,
"O' Allah (God), whoever gives me food, give them food;
whoever gives me drink, give them drink;
whoever shows kindness and mercy to me, be Kind to them too and be Always Merciful;
whoever makes me smile, bless their days with smiles;
whoever does good to me, O' Allah do good to them too."
Allah knows best.
TIP: When supplicating or making du'a (whether your du'a is for yourself, for a brother/sister-in-Islam, or for all Muslims) you don't have to say your du'as loudly so that others can hear what you're saying. Allah is the All-Knowing and All-Hearing who knows your innermost thoughts and feelings. So you don't have to be all "I want to make du'a for my hosts but I'm shy that they might hear me or if they hear me supplicating for them they might think I'm showing off."
Also, keep in mind that whenever you sincerely pray for a fellow Muslim, an angel near you always says something like 'for you likewise' meaning, the good du'a you prayed for your Muslim brother/sister will also be returned to you. Allah knows best.