15 month old significantly reduced fluid intake

Not a medical issue, he’s still peeing, but he’s been constipated and on MiraLAX for months so I’m stressed. Looking for any advice/similar stories. I assume it’s teething related, he’s not sick. He will nurse but I’m not making much anymore.

Things I’ve tried:

- new cups

- offering my cups

- weird vessels like lids of jars, bowls, spoons, etc.

- taking him outside hoping he’ll get hot and want to drink

- adding small amounts of juice

- leaving a cup out for him

- offering the cup every ten minutes or so (he’ll take sips)

- offering in the bath

- praise when he drinks on his own

This has been going on maybe 4-5 days. If this happened for your kid, how long til they started drinking normally again?