So I have a problem. My 2 year old has a viral infection. He also hasn't pooped in a couple of days.…

So I have a problem. My 2 year old has a viral infection. He also hasn't pooped in a couple of days. He's complaining of a tummy ache and we think that may be some of it. He isn't eating due to it but is drinking a lot of fluids which is great. My question is what can I do to help him poop? He really only wants water to drink which makes this harder too.