You can use contains (this works with an arbitrary sequence):
df.filter($"foo".contains("bar"))
like (SQL like with SQL simple regular expression whith _ matching an arbitrary character and % matching an arbitrary sequence):
df.filter($"foo".like("bar"))
or rlike (like with Java regular expressions):
df.filter($"foo".rlike("bar"))
depending on your requirements. LIKE and RLIKE should work with SQL expressions as well.