There is a random value function =RAND(). Put this in the first cell of a
spare column and copy down. Then you can sort the data on this column. Note
that you will get new random values every time the spreadsheet
recalculates - whenever you edit or do anything. If you want to keep one set
of random values, copy the column and Paste Values over the =RAND()
formulas.
You could use a helper column alongside your data and enter the formula
=Rand()
Drag the formula down to the last row of your data
Select your data and this new column and sort by the new column.