Create a new column to the right of the SKU No. column. Create a formula in the first cell (assuming your table starts at the top left of the spreadsheet):
=IF(B2="",C1,B2)
This basically says, if the cell to the right is blank, use the value from the cell above, otherwise, use the value from the cell to the left. Fill the formula down to the bottom of your table (e.g., select the cell & double-click the lower right corner of the cell) and, presto, you'll get the result you want. If you require it to be in the original column, you can copy the new column and Paste Special - values on top of the original column. Then you can delete the working column you created in the first step.
This assumes you have a value in the first row of the SKU No. column. If your table is located elsewhere on the sheet, you can use arrow-keys to get the coordinates of the cells to the right and above (in place of B2 and C1, respectively)