Are this vector icons? I'm working on a game and I want to make icon to learn technique how it's made, but so far I'm not sure how to make especially that glossing effect.
A good approach to learning a technique is to start by breaking down how another artist did it. The style above can easily be found on any of the large graphic asset markets. Creative Market, Graphic River, and Pixden are a few of the bigger ones.
Searching "game candy" on Creative Market quickly turned up many similar assets as the one you have. Here is an example.