Palatability is extremely important as he has (for good reason) resistance to many foods and textures that are far beyond pickiness. He is autistic, cognitively challenged, and a victim of past trauma including mental food insecurity and malnutrition (we adopted him through foster care) -- all of which add to his resistance to eating things he's unsure about. He eats inconsistently, so it's hard to get nutrients in through table food.
He accepts ice cream and smooth yogurt (no chunks), so if I could mimic those he might drink it. He was prescribed PediaSure and drank that all the time when he literally would eat no food for the first year with us, so something with that thick, milky texture seems OK.
It's best if it would go through a sippy cup. He has some oral and mental reasons that he gets most of his drinks through a sippy.
Sweet is probably more likely to be accepted. I have plenty of our own maple syrup and honey from our land if those would help.
We know of no allergies.