Bad breath in ds1(6) and ds2(1.5). water helps ?

[Oblomov]

My sil who is a nurse told me that she thought ds1 had bad breath. a while ago. she said he should drink more water. now we have ds2, his breath is stinky too. mind you mine isn't the best.
what can we do ?
is it true that they are not drinking enough ? do i need to cut out foods ?
what can you do other than tooth brushing ?

I found this;

Drink Plenty Water

A dry mouth represents the ideal home for odor causing bacteria which flourish in this type of environment. Saliva normally keeps the mouth moist. Additionally, saliva helps wash away the food particles bacteria feed on and dissolves odorous volatile sulfur compounds. Actions which dry the mouth or reduce saliva flow can increase bad breath odor

hth

But how much water is enough. I think he drinks a reasonable amount. maybe not ?

I believe its more to do with regular drinking of small amounts rather than a total iyswim

o.k. maybe not frequently enough then ? thank you . anything else that might help ?