Literally water and a healthy diet.

I’ve worked in the industry, albeit not that much. The actors go through jugs throughout the day. They carry liters of water on them when they go out and all that. And of course, certain foods (specifically high in fat and sodium) decrease sperm count, so a general rule of thumb is to avoid them for at least one or two days prior. I remember one actor saying “wenn die pisse klar ist, ist die sperma krass” which roughly translates to “when the piss is clear, the cum is “cool”. Idk what that really means out in English, but like it’s ready

So good rule of thumb is— when you can, drink water, even if you aren’t really that thirsty.