How does the military handle religious dietary requirements? An army runs on its stomach.
Which makes majority "Christian" faith the most conducive to military life.
Evangelical and majority Christian denominations: Eat anything at any time (aside from personal decisions to fast for a time). "For every creature of God is good, and nothing to be refused, if it be received with thanksgiving:" (1 Timothy 4:4)
As a Catholic Marine I looked at this issue this way; If I was in the field or forward deployed during Lent and Good Friday, I figured God would forgive me for eating meat on Friday because I really had no choice. From the time I enlisted in 1984 to about the late 90’s MRE’s didn’t have vegetarian or fish option. So unless your unit set up a field mess you ate what you got out of the box. I spent a lot of time in artillery units (11th Marines) so it was very rare that we got hot chow in the field.