My toddler drinks water mostly at night as she is allowed a water bottle in bed (in fact it's the only drink or food allowed in her room). We get the juice bottles that have character heads on them, they're usually no spill, and when she drinks all of the juice out, we just wash and fill it with water. During the day she requests other things, but if she sees me drinking water, then she usually asks for a sip. I don't ever share my drink with her, unless I'm drinking water. She also really likes water fountains. Anytime we go to a store or doctor and pass the water fountain, she wants to have a drink. It can get annoying at times, but I always let her have some sips when she wants water. So maybe introduce him to water fountains and see if he'll at least drink from there. Or offer him some of your drink when you're drinking water. If you do keep other drinks in the house, like juice or chocolate milk, fill their sippy with water and let them know they can't have the juice or chocolate milk until they drink all of the water from their cup. Good luck!