straightening bowed wood - Ikea drawers

Photo needed, not enough info

What about something like a sash cramp with the 'clamps' reversed to work as a spreader?

I'd take it apart and try to flatten the sides. Has to be easier than trying to do it while the unit is assembled.

Remove them to a less damp situation. Possibly use some straight lengths of 4x2 timber on the outside of each frame member. Put some packing between drawer frame and timber at top and bottom. Then one or more G clamps to *gently* persuade the frame that it's in the wrong place. This should work provided there is sufficient room for clamps. I have no experience of the units. Possibly an 'F' clamp where the clamp heads can be reversed to give outward pressure. I have seen such. Also possibly some pairs of sash clamp heads put into reverse duty, ie. pushing not pulling. However, if the timber frame is bowed it has become so for a reason. You may be able to make it more straight but equilibrium will prevail. Don't expect a quick fix. HTH Nick.

Dry them out and they may return to where you expect them to be. Proper drying out in a normal house will take weeks or months. Brought an oak table back from my late fathers house (centrally heated to about 25C 24/7) it had a large crack along the top 1/4 to

You don't say what these draw units are made from, real timber, faced both sides chipboard, faced one side chipboard(*). If timber leave them in the room they will be in for 6 weeks and see what they are like then.

(*) Or other composite material.

A screw jack can be as delicate as you like.