Suggestions for a 7.5-Hour Layover in Colombo: Negombo Beach, Food, and Shopping Tips?

I have a 7.5-hour layover at Colombo Airport from 4:00 PM to 11:30 PM in the first week of October. I was thinking of heading to Negombo Beach for an evening snack or an early dinner. We might also check out some churches on the way, if time permits.

I personally love shopping for food when I travel, like different types of chips, instant food, ready-to-eat items, savory snacks, frozen food, maybe some curry pastes to cook at home, and fridge magnets. However, since I don’t have much time, I won’t be able to taste/browse everything and decide what to bring back home, so I’d appreciate any suggestions on what to get and where to buy them.

Also, I'd love to try some famous Sri Lankan specialty foods and would appreciate recommendations for beach bars or restaurants in the area!