fruit juice works well, 2sp - mine love mango, peach, raspberry and pineapple, a tad of sugar (fructose) and a bit of gelatine to set. Even can do adult ones with gin and vodka added.
How about using milkshakes (banana, strawberry or chocolate) as in those 1 Litre cartons available from places like Iceland, Asda, etc,. They make delicious milkshake lollies.
Yoghurt's would work really well, as would fresh fruit juice. My Mum made ones with diluted orang squash for myself and my brothers when we were young in the 50's and 60's. Much cheaper than ones you bought in the shops.
You can actually freeze a banana successfully, so I would imagine that purée banana would work. Maybe add alittle sugar and lemon juice to stop it going brown.
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