Yes sonic can canonly surf and heres why i believe so. He surfs in the newest Sonic and Mario at the olympic games. One could argue that because its not a SEGA game it shouldnt be considered canon that he can surf. But heres the thing-

In the olympic games, sonic is seen wearing a life jacket when participating in the swim races. So nintendo is obviously aware of the fact Somic notoriously cant swim and added the life jacket to put emphasis on that. Also SEGA def has some say in the olympic games for sonic.

In the surfing contests though, Sonic is seen surfing WITHOUT a life jacket in the same game. So obviously, Sonic feels comfortable enough with surfing that he doesnt feel the need to wear a life jacket when doing so. Signifying hes pretty damn good at it too.

So in conclusion, Sonic not only can surf, but he probably really enjoys it too. Thank you for coming to my ted talk. Now stop commenting “SONIC CAN SURF?!?!”