Hi,

the code of method is a part of full source code so here is the original method:

/// <summary>
        /// Returns html code that represents payment option. Used for generating of invoice.
        /// </summary>
        /// <param name="dt">Table with the order data</param>
        /// <param name="currency">Currency info</param>
        /// <param name="renderDiscount">Render discount values</param>
        public static string GetProductList(DataTable dt, CurrencyInfo currency, bool renderDiscount)
        {
            if ((dt != null) && (dt.Rows.Count > 0))
            {
                StringBuilder sb = new StringBuilder();

                // Header
                sb.Append(" <table width=\"100%\" style=\"text-align: right\" cellspacing=\"0\" cellpadding=\"2\" class=\"productsList\">");
                sb.Append(" <thead><tr><th colspan=\"" + (5 + (renderDiscount ? 1 : 0)) + "\" class=\"headerBorder\"> </th></tr><tr>");
                sb.Append("     <th style=\"text-align: left;padding-left:2px\">");
                sb.Append(ResHelper.GetString("InvoiceTemplate.SKUName"));
                sb.Append("     </th>");
                sb.Append("     <th>");
                sb.Append(ResHelper.GetString("InvoiceTemplate.SKUUnits"));
                sb.Append("     </th>");
                sb.Append("     <th>");
                sb.Append(ResHelper.GetString("InvoiceTemplate.SKUPrice"));
                sb.Append("     </th>");
                if (renderDiscount)
                {
                    sb.Append(" <th>");
                    sb.Append(ResHelper.GetString("InvoiceTemplate.UnitDiscount"));
                    sb.Append(" </th>");
                }
                sb.Append("     <th>");
                sb.Append(ResHelper.GetString("InvoiceTemplate.Tax"));
                sb.Append("     </th>");
                sb.Append("     <th>");
                sb.Append(ResHelper.GetString("InvoiceTemplate.Subtotal"));
                sb.Append("     </th>");
                sb.Append("</tr></thead><tbody>");

                double value = 0.0;

                // Add the items
                foreach (DataRow dr in dt.Rows)
                {
                    string name = HTMLHelper.HTMLEncode(ResHelper.LocalizeString(Convert.ToString(DataHelper.GetDataRowValue(dr, "SKUName"))));

                    // If it is a product option
                    if (ValidationHelper.GetGuid(DataHelper.GetDataRowValue(dr, "CartItemParentGuid"), Guid.Empty) != Guid.Empty)
                    {
                        name = "  - " + name;
                    }

                    sb.Append("<tr>");
                    sb.Append(" <td style=\"text-align: left\">");
                    sb.Append(name);
                    sb.Append(" </td>");
                    sb.Append(" <td>");
                    sb.Append(Convert.ToString(DataHelper.GetDataRowValue(dr, "SKUUnits")));
                    sb.Append(" </td>");
                    sb.Append(" <td>");
                    value = ValidationHelper.GetDouble(DataHelper.GetDataRowValue(dr, "SKUPrice"), 0);
                    sb.Append(Ecommerce.CurrencyInfoProvider.GetFormatedValue(value, currency));
                    sb.Append(" </td>");
                    if (renderDiscount)
                    {
                        sb.Append(" <td>");
                        value = ValidationHelper.GetDouble(DataHelper.GetDataRowValue(dr, "UnitDiscount"), 0);
                        sb.Append(Ecommerce.CurrencyInfoProvider.GetFormatedValue(value, currency));
                        sb.Append(" </td>");
                    }
                    sb.Append(" <td>");
                    value = ValidationHelper.GetDouble(DataHelper.GetDataRowValue(dr, "Tax"), 0);
                    sb.Append(Ecommerce.CurrencyInfoProvider.GetFormatedValue(value, currency));
                    sb.Append(" </td>");
                    sb.Append(" <td>");
                    value = ValidationHelper.GetDouble(DataHelper.GetDataRowValue(dr, "Subtotal"), 0);
                    sb.Append(Ecommerce.CurrencyInfoProvider.GetFormatedValue(value, currency));
                    sb.Append(" </td>");
                    sb.Append("</tr>");
                }
                sb.Append(" <tr>");
                sb.Append(" <td colspan=\"" + (5 + (renderDiscount ? 1 : 0)) + "\" class=\"bottomBorder\"> ");
                sb.Append(" </td>");
                sb.Append(" </tr>");
                sb.Append(" </tbody>");
                sb.Append("</table> \n");

                return sb.ToString();
            }
            else
            {
                return null;
            }
        }

You can change the method to return requested html code. How to use custom providers is described here:
custom providers

Then you can overwrite the method in your custom order info provider.

Alternatively you could create a custom macro - that will return requested html code (example is in the middle of document):
http://devnet.kentico.com/docs/ecommerceguide/customizing_invoice_and_email_templates.htm

Best regards,
Ivana Tomanickova