M.R.
Around that age for my older one (who is 4 now), but I used to scoop some water in my hand and hold it over his mouth first and then he'd spit it all out. (Not choking or drowning him, but it gave him enough more in there that spitting felt easier I think.) My 2 1/2 year old still swallows no matter what I do, so he gets just a dab of toothpaste and a lot of water to drink afterwards.