What plugin/app do you use to animate your Sketch file?

Definitely Principle! Export your Artboards and just open them in Principle - done! Lots of animations, interactions, lots of options, just a great tool for putting together a prototype. UI is quite similiar to sketch, so everything feels familiar if you are a longterm sketch-user. At 129$ you get the perfect tool for turning your sketch artboards into animations and interactions.

Definitely a must have

It works inside the Sketch UI.

I just started using Diya. I like it so far. It exports to web prototypes, which makes sharing super easy.

Seamless import of Sketch files. Layers and contents stay intact and editable. Designing transitions and animations is such a breeze, it has a shallow learning curve.

Super easy and powerful. Very, very low learning curve, you'll master it in no time.

Kite is a great way to get more After Effects-style control and animations in a native Mac app experience.

Have you tried InVision Studio? It's in early access beta, and it'll import your Sketch file and let you add animation. You can also share it with folks via sharelink. It's pretty awesome.