With a flight time of around 45minutes, air travel is by far the most scenic and quickest way to travel from Colombo. The cheapest option is via Helitours, run by the Sri Lankan Airforce, costing just 4,650 LKR (roughly $25 USD). The commercial operators include Cinnamon Air and Fitsair and range between $100 - $250 USD
There is currently no direct highway to Trincomalee, so if you have some spare time (approximately 6 hours) on your hands, you can enjoy the scenery change as you literally traverse the island. Private drivers can usually be organized by all accommodation providers. Additionally, the apps Uber and Pickme offer country-wide services departing from ColomboBy Bus
All buses leave from Colombo’s main bus station Pettah, and arrive at Trincomalee’s main bus station in the middle of town. For the budget conscious, the cheapest way is via the public bus, costing just 462 LKR (roughly $2,50 USD), with a duration of around 6 hours. For a more comfortable experience, the Superline bus travels overnight, offers AC and a guaranteed seat upon reservation. This costs 1220 LKR (roughly $6.70 USD)
Train travel in Sri Lanka is extremely affordable. Tickets for Intercity and other Express Train Services to Trincomalee can be bought from Maradana Railway Station or Colombo Fort. First class, second class and third class are all available, which cost under 1000 lkr ($5.50 LKR). Travel duration is approximately 7.5 hours.