Sorry, shindy. I was completely joking – I have no idea “how much” is OK and I would imagine it varies by individual greatly.
Yank the Aussie: I juice fruits all the time. When I have a cold I squeeze every citrus I can find into a cup and drink it. But that has nothing to do with coffee. And as for Ginseng and Guarana – I don’t care if the molecular structure is exactly the same as coffee – that is the same argument that splenda uses to substitute itself for sugar. If you want to quote me the Rambam on “being shomer the guf” then avoid these products. Coffee is much less of a problem.