Is it permissible to visit people of innovation (Ahl al-Bid'ah) and to eat and drink with them?

There is no objection to visiting disbelievers for a legitimate Shar'i (Islamic legal) benefit, such as visiting them when they are sick. Indeed, the Prophet, may Allah bless him and grant him peace, visited a Jewish boy. It is also permissible to eat and drink with them if the food is permissible, and the Prophet, may Allah bless him and grant him peace, accepted an invitation from a Jew for a meal.