If you forgot to say Bismillah at the start بِسْمِ اللّٰهِ أَوَّلَهُ وَآخِرَهُ Bismillahi awwalahu wa akhirah In the name of Allah, at its beginning and its end.
After eating الْحَمْدُ لِلّٰهِ الَّذِي أَطْعَمَنِي هٰذَا، وَرَزَقَنِيهِ مِنْ غَيْرِ حَوْلٍ مِنِّي وَلَا قُوَّةٍ Alhamdu lillahil-ladhi at‘amani hadha, wa razaqanihi min ghairi hawlin minni wa la quwwah Praise be to Allah who fed me this and provided it for me without any power or strength of mine.
A guest’s du‘a for the host اللّٰهُمَّ بَارِكْ لَهُمْ فِيمَا رَزَقْتَهُمْ، وَاغْفِرْ لَهُمْ وَارْحَمْهُمْ Allahumma barik lahum fima razaqtahum, waghfir lahum warhamhum O Allah, bless them in what You have provided them, forgive them and have mercy on them.