[Oliver_W]

Sweet sales are usually arranged by someone outside of the charity who supports it, rather than the charity themselves.

For example, Doreen might go and buy one of those big things full of mini bags of sweets for £3, and sell each packet for 50p. She'd probably ask local shops to have one of those cardboard trays with a coin slot or something. This would raise (let's just guess) £20 every couple of weeks, which she then donates to the charity.

On her behalf, it's worth the effort because she's donating £17 more than she would have done without this. But for the charity themselves to do this, they'd have to specifically pay someone to do all this, and even a couple of hours a week at minimum wage would wipe out that £17.