Try this:

List<SoonestDrawDateModel> soonestDrawDateModel = new List<SoonestDrawDateModel>();

var realDrawDates = drawDates.ForEach(x => 
{
    soonestDrawDateModel.Add(new SoonestDrawDateModel() { CutOffDayId = x.CutOffDayId, DrawDay = x, DrawDayId = x.DayId});
    soonestDrawDateModel.Add(new SoonestDrawDateModel() { CutOffDayId = x.CutOffDayId, DrawDay = x, DrawDayId = x.DayId + 7});
}).OrderBy(y => y.DrawDayId);

Basically, this does the same as yours, but this iteration is more compacted.

Try this:

List<SoonestDrawDateModel> soonestDrawDateModel = new List<SoonestDrawDateModel>();

var realDrawDates = drawDates.ForEach(x => 
{
    soonestDrawDateModel.Add(new SoonestDrawDateModel() { CutOffDayId = x.CutOffDayId, DrawDay = x, DrawDayId = x.DayId});
    soonestDrawDateModel.Add(new SoonestDrawDateModel() { CutOffDayId = x.CutOffDayId, DrawDay = x, DrawDayId = x.DayId + 7});
});

var realDrawDates = soonestDrawDateModel.OrderBy(y => y.DrawDayId);

Basically, this does the same as yours, but this iteration is more compacted.

EDIT: It seems I messed up while pasting the code, sorry for that, this should work now, try it and let me know