Hydration is a big issue, especially for bowlers and batsmen on a long innings.
We usually have squash at 22 overs, but on very hot days move it to 15 and 30. I have regularly opened the bowling this season, often 10-12 overs straight, so also put a water bottle at fine leg, it's essential. I have taken to adding one of those electrolyte tablets to it, doesn't taste great but really helps.
As I edge towards 50 I am also finding I need to do plenty of stretching before and after the game to minimise heavy legs and stiffness that evening and next day.