You can check the .NET documentation on CultureInfo to see how to use its contructor.
If you always want the same format not matter what the local setting, try handling the DrawCellDisplayText event.
private void gridDataBoundGrid1_DrawCellDisplayText(object sender, Syncfusion.Windows.Forms.Grid.GridDrawCellDisplayTextEventArgs e)
{
if(e.Style.Format == "dd-MMM-yy" && e.Style.CellValue != null && e.Style.CellValue is DateTime)
{
DateTime dt = (DateTime)e.Style.CellValue;
e.DisplayText = dt.ToString(e.Style.Format, System.Globalization.CultureInfo.InvariantCulture.DateTimeFormat);
}
}