I echo Christine's recommendation for water. Simon had been diagnosed with nephritus several years before being diagnosed with the tonsil SCC so we were all very nervous for his kidneys with the chemo.

He drank at least 3 litres of water (with lemon juice) a day during his treatment. He came out of it with his kidney function at low normal (helped no doubt by his significant weight loss, as weight is one of the parameters used to calculate kidney function).

Even taking account of the weight loss his nephrologist thinks his kidney resiliance is "remarkable". Who knows why - maybe idiosyncratic, but I think (from a position of profound ignorance, no doubt) it's the water and the lemon juice (alkalanizing and anti-inflammatory).

Good luck with it all - it's a very tough treatment for anyone.