Which pluck did they use in Sias' Cheap Thrills?
Or how could one get a similar sound? Is it maybe included in a VST you can purchase?
It also depends on what DAW you use.
In FL studio, you can try with Fruity DX10.
In Ableton, you can search pluck sound from top search box.
To make it sounds similar as Cheap Thrills pluck, you might need a little high cut on the sound and add stereo reverb on that.
There are a lot of pluck sounds which come with third party plugins such as Nexus, slynth2, Hypersonic2, Massive and Serum.
If you would prefer sampling, you can pick Cheap Thrills pluck as a sample and load into Ableton sampler or whatever sampler plugin you like.
Check out this tutorial which is remaking cheap thrills track.