Short answer: at 6 months, look for a small-capacity cup (around 2oz) with a soft rim and a stable, weighted base — full-size cups overwhelm small hands and turn every practice sip into a soaked bib. Olababy's First Cup ($9.99, 2oz) is sized specifically for this stage; the Silicone Training Cup ($12.99) is the natural next step once a baby is sipping confidently.

Why start open-cup practice this early

Pediatric feeding specialists encourage introducing open-cup drinking from around 6 months — the same age solids typically start — rather than waiting until a toddler already has strong sippy-cup habits to unlearn. Practicing early builds the lip, tongue, and jaw coordination that open-cup drinking requires, before a spouted cup becomes the default.

What actually matters at 6 months

• Small capacity. A practice-size pour (around 2oz) means less liquid to manage per attempt and less mess when it goes wrong — which it will, often.
• Soft, gum-safe rim. A soft silicone rim is kinder to a 6-month-old's gums (and any emerging teeth) than a hard plastic or glass rim.
• A base that resists tipping. Babies this age have limited hand control — a low, weighted, or wide base reduces spills from an unsteady grip.
• Light weight. A cup a baby can actually lift and hold with two hands leads to more successful sips than one they can't manage.

Sizing up as skills grow

Once a baby is reliably sipping from a 2oz cup, sizing up to a larger open cup (Olababy's Silicone Training Cup holds more volume with the same soft-rim, weighted-base approach) extends the same skill without resetting to a spouted sippy cup. The goal at every stage is the same: an open-cup shape, sized to what a baby can actually manage right now.