Here {$x$} denotes the fractional part of x
When $x\rightarrow0^+$, $\{x\}=x$. (Since $x$ will be a very small number example: $0.000000000001,$ it will not have an integer part, and the fractional part will be equal to the number).
When $x\rightarrow0^-$, $\{x\}=1+x$
So $\displaystyle\lim\limits_{x\rightarrow0^+}\frac{\sin\{x\}}{\{x\}}$ simplifies to $\displaystyle\lim\limits_{x\rightarrow0^+}\frac{\sin x}{x}=1$
And $\displaystyle\lim\limits_{x\rightarrow0^-}\frac{\sin\{x\}}{\{x\}}$ simplifies to $\displaystyle\lim\limits_{x\rightarrow0^-}\frac{\sin (x+1)}{x+1}=\sin1$
So it's discontinuous
Edit: Made corrections as suggested in the comments
For $x \in [0,1)$ we have $\{x\} = x - \lfloor x\rfloor = x-0 = x$, but for $x \in [-1,0)$ we have $\{x\} = x- \lfloor x \rfloor = x - (-1) = x+1$.