The nipple and bottle of this soft breast-shaped bottle are all one piece, so to fill the bottle, you unscrew the bottom, flip it over, and fill it up. It comes with a cap (not shown), so no milk will spill during this process.

Testers said: "My baby had no qualms. She stuffed it in her mouth and sucked away. But if the teat gets ripped (it's very soft) or you need a different flow rate, you have to buy a whole new bottle because of the design."

$13, Adiri, Right Start

Because it is smartly encased in a rubber sleeve, this glass bottle can be given to your kid or thrown into your diaper bag without fear of breakage.

Testers said: "Using glass gives me the most peace of mind, and it is a better insulator than plastic."

$18, Baby Life

These bottles have wide necks and a special venting system to help reduce gas. The extra soft nipples are made of high-grade silicone and meant to help ease the transition from breastfeeding to bottle-feeding.

Testers said: "The shape was easy for my six-month-old to hold himself, and the nipples are very, very soft. But I don't understand how the skinny piece of plastic hanging from the inner rim of the nipple helps ventilation."

from $17 for two 5-ounce bottles, Thinkbaby, Giggle

Not only are Born Free's products made from safe plastic, the bottle also has a special air vent to help reduce air bubbles and eliminate colic symptoms.

Testers said: "The bottle is fantastic. The hourglass shape is easy for little hands to grip, and the air vent is a feature you can't find in any of the others. But the cup is a bit of a pain. The low-flow nipple is so tight that it's hard to get liquid out, and the fast-flow is so soft that the kids left trails of milk all over the house."

From $19 for two five-ounce bottles, Born Free

Made from double-walled stainless steel, this cup is designed to keep beverages cold for up to six hours. The steel is also strong enough to handle any sort of abuse a kid might put it through.

Testers said: "It isn't easy for the kids to spill milk out of, but it is very easy for them to drink out of."

$15, Thermos

The unique round shape allows kids to comfortably hold the cup with two hands. The spout is also angled, so they don't have to tip their heads too much while drinking.

Testers said: "This one is great because it doesn't have that quasi-stopper that prevents liquid from flowing too fast—which makes it easier to clean. My kids love the shape so much that the one who has it is the envy of the other. The only possible drawback is that it doesn't fit into cup holders on car seats or strollers."

$6, Boon

This sporty steel design is super-lightweight at just four ounces. The sippy-cup adapter top comes with two spouts, but this cup can also be used as a regular water bottle.

Testers said: "It might not be the best for kids who are just starting to use a sippy cup, because it has to be tilted quite a bit. But it is good at keeping the liquid from spilling."

$18, Klean Kanteen

Not only are these non-toxic steel bottles super durable and leak-proof, they come in tons of colorful and cute designs—144 to be exact with 22 interchangeable lids.

Testers said: "The bottle keeps liquids very cold. Having only two pieces makes it easy to clean, and the lid is attached to the bottle so it's impossible to lose it. The top locks closed, and the lid covers the top so it is practically impossible to spill—a great option for traveling. "

from $16, Sigg

Pour in the milk, then stick the cup in the fridge or freezer for at least half an hour. The insulation will keep it colder longer than a regular sippy cup would.

Testers said: "It's cute and doesn't present any cleaning or spilling problems. The kids have an easy enough time drinking from it, too."

$6, Munchkin, amazon.com