Is printing an emoji on tee shirts and selling them copyright infringement if the emoji font is under the Apache open source license?
On first reading, the question doesn't make any sense!
Apache licence is for software.
But you're asking about using a font.
Is a font technically software?
I think the answer would depend on how you classify the font in question.
If it is just a set of mathematical equations, which, at the end of the day, simply transforms user input to machine output, then using said font for T-shirts is not much different than writing proprietary software in an editor like emacs.
If it's just a set of images/pictures (or if you're printing a single character at such a large scale as for it to be possible to re-enact the original non-trivial mathematical description that would result in an exactly identical character to be produced by the same software in question), then you might be subject to whatever terms are specified in the licence for copying or distributing pieces of software in binary form.