The Bannsiders have been fined £200 by the association for breaching Article 33 of the IFA Disciplinary Code following last month's home game against Glentoran.
Items were thrown at visiting goalkeeper Aaron McCarey, and McKendry labelled the behavious "unacceptable" and said it was costing the club "money and reputational damage".
“This form of behaviour is totally unacceptable," a statement on the club website read.
“It is costing the club money and reputational damage and it is a shame the actions of a small minority of people means we have been fined.
“We have enjoyed healthy attendances at The Showgrounds so far this season and we won’t accept behaviour like this.”
Coleraine FC also stressed the importance that supporter misconduct must be avoided – including sectarian chanting to stop – as the club runs the risk of even costlier punishments being imposed.