Juice keeps the sugar but loses most fiber and food structure. Whole fruit is consistently associated with better outcomes than juice.
Evidence & sources
Greater whole fruit consumption was associated with lower type 2 diabetes risk, while greater fruit juice consumption was associated with higher risk. Evidence: moderate. Known: Three large prospective cohorts. Unknown: Observational. Source: Muraki et al., BMJ, Fruit consumption and risk of type 2 diabetes (2013).