What determines the sex of hybrid offspring?
I am detecting a bit of confusion in you wording of Haldane's rule.
Haldane's rule makes predictions on the fertility of offspring from an inter-specific cross, not the sex-ratio of the offspring from the cross.

"if inter-specific hybrid offspring are sterile, then the sterile offspring will be of the heterogametic sex."

In inter-specific crosses there is not an effect on sex-ratio of the resulting offspring, but a effect on the ability of the F1 offspring to reproduce.
For the offspring, those of the heterogametic sex, males in mammals (XY) and females in birds (ZW) will be sterile while the homogametic offspring will not be affected by hybrid sterility.