It has been claimed a member of the public complained to police about the incident in North East Fife yesterday.
A spokesman for the Scottish Liberal Democrats said: "Parties are not permitted to give away treats for voters. It shows how desperate the SNP are."
But the SNP dismissed the claims, insisting the snacks were for campaigners in Newport-on-Tay.
Campaign leader for the seat, Jenny Gilruth MSP, said the Liberal Democrats were 'panicking'.
"Their claims are absolute mince," she added.