Most modern packs are bladder-friendly. Many older packs can be made to do so, even if they did not have bladder compatibility in mind when designed.
The trick is to make sure a sheet frame is installed in one's small pack. Doing wo will greatly aid load-carrying capacity, and user comfort.
For the most part, bladders require a shallow depth compartment into which they can be inserted, and so stay upright, and useable. Some packs, not having such, can use the integral radio pouch to contain a differently dimensioned bladder to good effect.
If one's pack lacks such an internal compartment, capable of supporting a typical bladder, there are many external bladder carriers available.
As time goes by, and bladder failures happen, I have come to appreciate the old, indestructible, 1 Qt GI canteens. The conformal canteen cups and stoves add some value to this approach.
YMMV.