Is it illegal to feed stray dogs in Sri Lanka.

It is absolutely not illegal to feed stray dogs anywhere in Sri Lanka and many highly compassionate locals do it daily. However you must be incredibly mindful of the exact location. If you feed a stray dog directly near the entrance of your luxury hotel or right next to a busy beach cafe the dog will constantly return there later and aggressively beg from other tourists causing a massive nuisance for the business owners. If you want to feed them safely walk a substantial distance down the beach completely away from the crowded tourist zones and leave the food on the sand quietly.