Where condition for joined table in Sequelize ORM

Wrap the columns which reference joined tables in $$

A.findAll({
    where: {
        $or: [
            {'$B.userId$' : 100},
            {'$C.userId$' : 100}
        ]
    },
    include: [{
        model: B,
        required: false

    }, {
        model: C,
        required: false
    }]
}); 

Add the where condition in the include, along with join.

    {
       model: C,
       where: {
        id: 1
       }
   }