I haven't been involved in fund raising yet but I can tell you which ones do the best at my workplace where we get inundated with fundraising throughout the year.

Freddos - they sell like hotcakes. They sell for $1 so pretty much everyone has $1 to spare. Some people like me will buy 5 or 6 at a time to stash in their drawer. The mixed boxes work best - peppermint, plain, strawberry, caramello koala etc. I think you have to buy full boxes and then the mums have to mix them. The other chocolate ones that cost $3 take way longer to sell.

Another good one we had a few years back was slices - like lemon, peppermint etc. They came in a great plastic container. Because it was unusual a lot of people around the office bought them.

Haven't seen it done in many years but the lamington drives always used to be very popular as everyone loves them.