I've tried a hydration pack but unfortunately for me if I carry weight on my back or in my jersey pockets (think spare bottles of water) my lower back gets debilitatingly soe within only a few kilometers/miles.

When touring or even riding on hot days I use stainless steel Thermoses in my water bottle cages and keep a small clear water bottle in the handlebar mounted water bottle cage. I drink from the small water bottle and the replenish it from a stainless steel Thermos.

If my bike doesn't have a handlebar mounted cage I then use a toe-strap wrapped around the stem and over the handlebar to hold the small water bottle. Like this.



Cheers