Answered by: Maulana Maruf Ahmed
Is a Muslim man obliged to eat with a right hand according to Sunnah even if he’s left-handed?
بسم الله الرحمن الرحيم
It is greatly encouraged to eat and drink using the right hand. Refusing to do so whilst one is able is considered to be somewhat disliked. 
The Prophet (sallallahualaihiwasallam) ate with a man who was using his left hand. The Prophet (sallallahualaihiwasallam) said to him, “Eat with your right hand.” He said, “I cannot.” He (sallallahualaihiwasallam) said, “Then you never can.” Only pride had stopped him and he could not raise it to his mouth.
However, if one has a genuine difficulty in using the right hand, it is not disliked to use the left hand. 
If someone is left handed but has no difficulty in using the right hand to eat and drink, the right hand should therefore be used.
Only Allah knows best.
Written by Maulana Maruf Ahmed
Checked and approved by Mufti Mohammed Tosir Miah
Darul Ifta Birmingham
 Ibn Nujaym: Al-Bahr Al-Ra’iq, vol. 1 pg. 56 Dar al-Kitab al-Islami
 Sahih Muslim, Hadith no. 2021
 Al-Aini: UmdatulQari, vol. 21 pg. 28, Dar Ihya al-Turath al-Arabi, Beirut
This answer was collected from DarulIftaBirmingham.co.uk, which is run under the supervision of Mufti Mohammed Tosir Miah from the United Kingdom.