Growing up on military bases, Jim had easy access to bowling alleys. Jim's dad bowled in military leagues and (coincidentally) now works for a bowling ball manufacturer.
Around two and half, we took Ranger bowling for the first time. He loved it. We've gone a few times since.
Last night Ranger kept mentioning bowling, so we dug through the recycle bin for some impromptu pins.
Our Simply Lemonade containers are ideal choices. We all prefer them upside-down because it improves the chain reactions and delivers a very satisfying clatter when they fall. The lids are heavy enough that Ranger has no problem setting them up on our own.
Other bottles that worked well are water bottles, shampoo bottles, and half gallon juice bottles. Milk gallons will work, but don't provide much satisfaction in sound or tumbling action when hit.
We used a foam ball, a spherical soccer ball pillow, and a rubber ball. All the balls worked well, so it looks like you could use any ball that fits your toddler's hands well and isn't too heavy.
We think soda bottles would work well, but didn't have any on hand to test.
These impromptu bowling sets can make an easy and cheap activity for entire herds of toddlers.
It's always fun to find toys in the recycling bin: check out our homemade milk-carton building blocks. (They'll also do substitute bowling pins in a pinch.)