Srilanka in 4 -5 days ideal days to explore srilanka
day 1 uh can land colombo then from where uh can hire a taxi and go directly to kandy the cultural capital of srilanka best attractions were the temple to the tooth, uh can enjoy there nature walk jungle safari etc.
day two uh can go to nuwara eliya its famous for oldest tea estate of sri lanka.
day 3 bentota beach here uh can do water sports activities
day 4 colombo visit the city at ur own lesiure uh can do shopping, clubbing, museum visit etc
You can enjoy a lot if you go with your friends
activities to do
water sports(scuba diving, snorkeling,rafting,water skiing,etc)
night life in Colombo( pub,casino, restaurant)
temples (gangramaya) in Colombo
you can see sunrise at kandy lake in Kandy
you can visit temple of tooth relic
take a train ride from kandy-ella where you can see nature's beauty going through mountains and tunnels, different types of plantations.
you can climb sigiriya rock fortess.
you can write letter to your family and friends from one of the world's oldest post office Nuwara Eliya Post Office.
Sri Lanka is a beautiful country. I was there for 20 days and still couldn't cover all. Small country with lot to see. Colombo, Kandy, Galle and Yala National Park are very famous along with Jaffna but not enough. if you feel like advise me to ask friend for paid service.
Since others hv already suggested Colombo-Kandy-Nuwara Eliya, I will suggest the other side of Srilanka.... Our itinerary was 2 nights Colombo 2 nights Bentota beach and 1 night Hikkaduwa beach... u can travel by the local trains from one place to the other... so if u are a beach and seafood lover then go for it.