Baker's yeast ferments significantly faster than brewer's yeast. It will still make alcohol and co2, but it will add a yeasty, bread-like flavor. For cider, this flavor may be over-powered by the apples and it won't be so bad. Brewer's yeast will be much slower, but better.
FWIW, you can also make bread with brewer's yeast if you don't mind waiting days for your bread to rise