The answer is yes, in fact the sequence $S\subset \mathbb{N}$ indexed by [Thue-Morse sequence](https://en.wikipedia.org/wiki/Thue%E2%80%93Morse_sequence) works, see [this MO question](https://mathoverflow.net/questions/87923/sequences-without-long-arithmetic-progressions). Note that this sequence is syndetic because it contains one of $\{2n, 2n+1\}$ for every $n$. You can extend to the negatives by reflecting and trivially only lose a factor of two on $\ell$.