C2H4 is not capable of hydrogen bonding because the H's are attached to the Carbon, and the charge is 0.
Although HCl cannot hydrogen bond, that aspect does not hinder it's ability to dissolve. Because HCl is polar and so is water, the positive side of H2O will be attracted to the negative side of HCl, thus "tearing" the molecule apart. (Like dissolves like - polar dissolves polar)
Based on the Solubility rule, KBr is soluble because it contains a group 1 metal.
