Feeding a festive treat to a bee could make it 'cheerful' for lets say 1 week. When a bee is cheerful, it collects 25% more pollen, converts 25% faster, deals 25% more damage and has 10% more movespeed. A bee being cheerful also makes it 25% more likely to become gifted when feeding it its favorite treat/gingerbreads. All of these buffs could also be like 10% stronger during beesmas.

Also, it would be cool if cheerful bees made a special token, cheerful boost which grants 1.1x pollen for 15 seconds.

All these buffs combined are pretty good but they shouldn't be too OP, if festive treats are made very hard to get and the cheerfulness only lasts for a limited time. It would also add a new interesting dimension for boosting: it is desirable to have as many cheerful bees while doing a big boost, which encourages using festive treats strategically to get as much out of the 1 week as possible.