mostly just water but if I need electrolytes I’ve found most pre-made powders, tablets, or drinks are too sweet, more so if they use alternative sweeteners like Stevia. so, I found a place that sells electrolyte powder, unsweetened and unflavoured, and mix it up myself with some water, lemon juice, and a bit of Stevia. much better than the premade mixes.
although I do like pocari sweat as a rare thing. you can buy that as a powder online, but the local asian market sells cans of it so I keep a few around.
If looking for a Linux or Windows laptop, this is the right answer. Look for one of these used, and get the highest spec model in your budget. I’ve still got ThinkPads from 2012 kicking around running Linux that are perfectly capable light duty machines, not that I’d go that old if it was my primary laptop.