Irony is a very difficult thing to translate. The irony in your example is in the fact that every day ends in 'y', in the English language that is. To create a seamless true natural translation it's necessary to identify a commonality amongst all of the days or another entirely different scenario which has no association with time. Spanish has a lot of Catholicism attached to it so it's very likely that a decent translation could be formed from something in that religious context.
So, what happens every day in a Catholic lifestyle that is taken for granted? And how can you keep the translation of such an event from being stereotypical? Anti-ethical? Offensive?
Sólo pesco en los días que yo coma una tortilla.
I used the subjunctive to make it as if eating one might be unlikely, which is unlikely in itself. Tortillas are a daily thing from my experience.
Sólo me tomo cúando respiro.
The irony is that I breathe all the time.
You really have to pick your poison when it comes to translating irony. There is always that possibility of actually saying something that is indeed offensive, or embarrassing, or outright stupid.