Well, I found out yesterday that a jar of the dolmio bolognese sauce is only 5½ syns, so if you CBA making your own, that's a nice low-syn option.
Or if you fancy something ricey, the uncle bens risotto pouches are quick and easy - I like the tomato and herb one for 6 syns.
Not too sure on anything that's tesco own brand - I tend to make stuff from scratch where I can, just so I can keep syns for chocolate!!!